| probing the role of c-1 ester group in naja naja phospholipase a2-phospholipid interactions using butanetriol-containing phosphatidylcholine analogues. | to understand the role of the ester moiety of the sn-1 acyl chain in phospholipase a2-glycerophospholipid interactions, we introduced an additional methylene residue between the glycerol c1 and c2 carbon atoms of phosphatidylcholines, and then studied the kinetics of hydrolysis and the binding of such butanetriol-containing phospholipids with naja naja phospholipase a2. hydrolysis was monitored by using phospholipids containing a nbd-labelled sn-2 acyl chain and binding was ascertained by measur ... | 1999 | 10092841 |
| in situ hybridization and immunohistochemical analysis of the expression of cardiotoxin and neurotoxin genes in naja naja sputatrix. | secretory processes and their regulation have been extensively studied in mammalian salivary parotid glands. however, little is known regarding the secretory mechanism in the venom glands of snakes, which invariably produce one of the most complex of all animal secretions. the pharmacologically important and toxic components of the malayan spitting cobra (naja naja sputatrix) venom include postsynaptic neurotoxins (ntx), presynaptic neurotoxins (phospholipase a2, pla2), and cardiotoxins (ctx) wh ... | 1999 | 10082757 |
| postsynaptic alpha-neurotoxin gene of the spitting cobra, naja naja sputatrix: structure, organization, and phylogenetic analysis. | the venom of the spitting cobra, naja naja sputatrix contains highly potent alpha-neurotoxins (ntxs) in addition to phospholipase a2 (pla2) and cardiotoxin (ctx). in this study, we report the complete characterization of three genes that are responsible for the synthesis of three isoforms of alpha-ntx in the venom of a single spitting cobra. dna amplification by long-distance polymerase chain reaction (ld-pcr) and genome walking have provided information on the gene structure including their pro ... | 1999 | 10077532 |
| benzophenone-type photoactivatable derivatives of alpha-neurotoxins and alpha-conotoxins in studies on torpedo nicotinic acetylcholine receptor. | by chemical modification of different lysine residues, benzoylbenzoyl (bzbz) groups were introduced into neurotoxin ii naja naja oxiana (nt-ii), a short-chain snake venom alpha-neurotoxin, while p-benzoylphenylalanyl (bpa) residue was incorporated in the course of peptide synthesis at position 11 of alpha-conotoxin g1, a neurotoxic peptide from marine snails. although the crosslinking yields for iodinated bzbz derivatives of nt-ii and for bpa analogue of g1 to the membrane-bound torpedo californ ... | 2014 | 10071785 |
| structure and organization of the cardiotoxin genes in naja naja sputatrix. | we report the genomic structure, organization and the presence of multiple isoforms of the gene encoding cardiotoxins (ctx) of naja naja sputatrix. the cardiotoxin gene consists of six ctx isoforms, each (2.2 kb) having three exons and two introns. two possible transcription initiation sites as well as consensus tata boxes and transcription factor binding motifs, ap-2, nfil-6/c/ebp, nf-kappab and puf have been identified in the 5'-region of the gene. the ctx gene isoforms show nucleotide variati ... | 1998 | 9738945 |
| structures of two novel crystal forms of naja naja naja phospholipase a2 lacking ca2+ reveal trimeric packing. | three crystal forms of naja naja naja phospholipase a2 were discovered through random crystallization screening, including two heretofore uncharacterized forms. the crystallization conditions for both of these novel crystal forms are ca(2+)-free whereas previously reported conditions include ca2+. one of the new crystal forms has a cubic lattice in the space group p2(1)3 (a = b = c = 69.24 a), the other has an orthorhombic lattice in the space group p2(1)2(1)2(1) (a = 67.22 a, b = 73.48 a, c = 8 ... | 1998 | 9636712 |
| labeling of torpedo californica nicotinic acetylcholine receptor subunits by cobratoxin derivatives with photoactivatable groups of different chemical nature at lys23. | different photoactivatable derivatives of toxin 3 (ctx) naja naja siamensis were obtained after ctx reaction with n-hydroxysuccinimide esters of p-azidobenzoic, p-azidotetraflourobenzoic, p-benzoylbenzoic and p-[3-(trifluoromethyl)-3h-diazirin-3-yl]benzoic acids. the ion-exchange hplc profiles for the reaction products were very similar in four cases, with one predominant peak corresponding to the derivative containing the label at lys23. after [125i]iodination, ctx photoactivatable derivatives ... | 1998 | 9578481 |
| zanhasaponins a and b, antiphospholipase a2 saponins from an antiinflammatory extract of zanha africana root bark. | a meoh extract from z. africana was examined for topical antiinflammatory activity and proved to be active against arachidonic acid (aa) acute edema, 12-o-tetradecanoylphorbol 13-acetate (tpa)-induced chronic inflammation, and oxazolone delayed-type hypersensitivity in mice. the extract also showed significant inhibitory activity of naja naja phospholipase a2 when a polarographic method was used. two oleanane-type triterpene saponins, zanhasaponins a (1) and b (2), and the cyclitol pinitol (4), ... | 1997 | 9392883 |
| naja naja cobra bite. | most venomous snakes in the united states are of the crotalidae family. another family of snakes, the elapidae, are not so common, but their bites may be a threat to zoo keepers and persons who have exotic snakes as pets. because elapidae envenomation is not common, signs and symptoms of such envenomation may not be recognized. elapidae venom, because of a curare-like property, can produce respiratory compromise followed by death within 10 minutes. antivenin, cholinesterase inhibitors, and mecha ... | 1997 | 9288976 |
| effect of lipid composition on lipoprotein lipase activity measured by a continuous fluorescence assay: effect of cholesterol supports an interfacial surface penetration model. | the breakdown of normal substrates by lipases requires an interfacial binding step prior to hydrolysis. interfacial binding and subsequent hydrolysis will be affected by the lipid components and hence physical properties of the substrate surface. in order to investigate in detail the effect of lipid structure on the activity of lipoprotein lipase (lpl), triolein-containing emulsion particles of defined composition have been used as substrates. in addition, lipase activity has been measured using ... | 1997 | 9032472 |
| [secondary structure and conformational heterogeneity of naja naja oxiana cytotoxin ii]. | the proton resonances of cytotoxin ii from naja naja oxiana were sequentially assigned in 2d 1h nmr spectra for all of its 60 amino acid residues of both major and minor components of the spectra. the presence of the minor component was shown to be due to a conformational heterogeneity of the cytotoxin. the proton-deuterium exchange rates of amide groups were measured in 2h2o at a ph of 5.0 and at 10 degrees c. experimental data obtained (d-connectivities, h-nc alpha-h coupling constants and lon ... | 1996 | 8929219 |
| taxonomic changes and toxinology: systematic revisions of the asiatic cobras (naja naja species complex) | until recently, all asiatic cobra populations were regarded as belonging to one single species, naja naja. recent revisions have shown that there are in fact at least 10 full species of asiatic naja. in order to allow the existing literature to be reconciled with these recent discoveries, an interpretation of the older nomenclature is provided. problematic areas, especially concerning the species n. sumatrana and n. siamensis, are highlighted. | 1996 | 8735239 |
| liver class-i alcohol dehydrogenase isozyme relationships and constant patterns in a variable basic structure. distinctions from characterization of an ethanol dehydrogenase in cobra, naja naja. | the major ethanol dehydrogenase of cobra liver was characterized in order to clarify isozyme relationships and functional motifs of the vertebrate enzyme. the cobra protein is a class-i form, most related to one of the isozyme subunits (the a form) in uromastix (lizard) liver. this positions the isozyme duplication and defines the main-line alternative. the new structure also allows extensive correlations with structure/function relationships for alcohol dehydrogenases in general, of which 38 an ... | 1996 | 8612631 |
| [refinement of the spatial structure of neurotoxin ii from naja naja oxiana venom]. | a set of 19 conformations of the neurotoxin ii from naja naja oxiana was determined by conformational energy minimization using constraints derived from experimental 1h nmr data. the pairwise average root-mean-square deviations were 0.86 a for the backbone heavy atoms and 1.48 a for all heavy atoms of these conformations. a model of the neurotoxin ii dimer is proposed to account for the relatively slow deuterium exchange rates of the val45 and leu51 amide protons, which are exposed to the solven ... | 1995 | 8540898 |
| photolabeling reveals the proximity of the alpha-neurotoxin binding site to the m2 helix of the ion channel in the nicotinic acetylcholine receptor. | a photoactivatable derivative of neurotoxin ii from naja naja oxiana containing a 125i-labeled p-azidosalicylamidoethyl-1,3'-dithiopropyl label at lys-25 forms a photo-induced cross-link with the delta subunit of the membrane-bound torpedo californica nicotinic acetylcholine receptor (achr). the cross-linked radioactive receptor peptide was isolated by reverse-phase hplc after tryptic digestion of the labeled delta subunit. the sequence of this peptide, delta-(260-277), and the position of the l ... | 1995 | 7543679 |
| synthesis of nitrodiazirinyl derivatives of neurotoxin ii from naja naja oxiana and their interaction with the torpedo californica nicotinic acetylcholine receptor. | five singly modified nitrodiazirine derivatives of neurotoxin ii (nt-ii) from naja naja oxiana were obtained after nt-ii reaction with n-hydroxysuccinimide ester of (2-nitro-4-[3-(trifluoromethyl)-3h-diazirin-3yl]phenoxy)acet ic acid followed by chromatographic separation of the products. to localize the label positions, each derivative was first uv-irradiated and then subjected to reduction, carboxymethylation, and trypsinolysis. tryptic digests were separated by reversed phase-hplc, the labele ... | 1995 | 7662107 |
| a new class of photoactivatable and cleavable derivatives of neurotoxin ii from naja naja oxiana. synthesis, characterisation, and application for affinity labelling of the nicotinic acetylcholine receptor from torpedo californica. | a new series of photoactivatable and cleavable derivatives of neurotoxin ii from the cobra naja naja oxiana is investigated which can be used for mapping the surface topology of the nicotinic acetylcholine receptor from torpedo electric tissue. the preparation and characterisation of five toxin derivatives, each with a radioactive 125i-azidosalicylamidoethyl-1,3'-dithiopropyl group in a defined position within the primary structure, are described. the photoinduced cross-linking reaction of the t ... | 1995 | 7737199 |
| [fragments 183-198 and 125-145 of the alpha-subunits of the torpedo californica nicotinic acetylcholinergic receptor binds alpha-bungarotoxin and neurotoxin ii from naja naja oxiana]. | interaction of the mono[125i]iodinated alpha-bungarotoxin and neurotoxin ii naja naja oxiana with the synthetic peptides corresponding to the fragments of the alpha-subunit of nicotinic acetylcholine receptor from torpedo californica was studied. it was found that both toxins bind to the fragments alpha 186-198, alpha 183-198 and alpha 125-145 adsorbed to the 96-well p.e.t.g. assay plates (costar). acm-groups on cys residues did not prevent toxin binding by the peptides studied. determination of ... | 1995 | 7748208 |
| [structure of peptide fragments of the complex (lys(abz)26) neurotoxin ii from naja naja oxiana cross-linked with the nicotinic acetylcholine receptor from torpedo californica]. | after irradiating the acetylcholine receptor complex with the title neurotoxin derivative, the labeled delta-subunit was separated by preparative sds-page, reduced-carboxymethylated and cleaved with lysc endoproteinase. one of the radioactive peptides isolated by hplc was further purified by electrophoresis in a tricin gel. edman degradation of the radioactive fractions yielded the sequence of the delta-subunit fragment starting from phe148. the aspn-cleavage of the radioactive peptide from the ... | 1994 | 7826405 |
| relationship between the binding sites for an alpha-conotoxin and snake venom neurotoxins in the nicotinic acetylcholine receptor from torpedo californica. | photoinduced cross-links between the iodinated lys26-p-azidobenzoyl derivative of neurotoxin ii from naja naja oxiana cobra venom and nicotinic acetylcholine receptor from torpedo californica (achr) have been studied in the presence of alpha-conotoxin gi from the marine snail c. geographus. preincubation of the achr-enriched membranes with increasing concentrations of alpha-conotoxin gi protects first the gamma subunit from photolabelling and then the delta subunit, the ic50 values being 0.76 an ... | 1994 | 7801351 |
| the three-dimensional nmr solution structure of α-cobratoxin at ph 7.5 and conformational differences with the nmr solution structure at ph 3.2. | abstract the 3d solution structure of α-cobratoxin, a neurotoxin purified from the naja naja siamensis snake venom, has been determined by nuclear magnetic resonance spectroscopy, in conjunction with distance geometry and restrained molecular dynamics, at ph 7.5. a total of 490 distance restraints were obtained from noe intensities and 25 φ dihedral angle restraints deduced from j- coupling data. the generated structures are well defined with root mean square deviations from a geometrical mean s ... | 1994 | 22671905 |
| the three-dimensional nmr solution structure of alpha-cobratoxin at ph 7.5 and conformational differences with the nmr solution structure at ph 3.2. | the 3d solution structure of alpha-cobratoxin, a neurotoxin purified from the naja naja siamensis snake venom, has been determined by nuclear magnetic resonance spectroscopy, in conjunction with distance geometry and restrained molecular dynamics, at ph 7.5. a total of 490 distance restraints were obtained from noe intensities and 25 phi dihedral angle restraints deduced from j-coupling data. the generated structures are well defined with root mean square deviations from a geometrical mean struc ... | 1994 | 7848557 |
| interaction of protein ligands with receptor fragments. on the residues of curaremimetic toxins that recognize fragments 128-142 and 185-199 of the alpha-subunit of the nicotinic acetylcholine receptor. | using a solid-phase assay, we found that 3h-labeled alpha cobtx from naja naja siamensis, a long-chain curaremimetic toxin, and 3h-labelled toxin alpha from naja nigricollis, a short-chain toxin both bind specifically but with substantially different affinities (kd = 4 x 10(-7) m and 50 x 10(-6) m) to fragment 185-199 (t alpha 185-199) of the alpha-subunit of the acetylcholine receptor (acchor) from torpedo marmorata. then we show that monoderivatizations of residues common to both long-chain an ... | 1994 | 8307203 |
| comparison of refolding patterns of erabutoxin b and cardiotoxin 3.10.2 from snake venom. | the refolding patterns of erabutoxin b (a neurotoxin) and cardiotoxin 3.10.2 (from naja naja siamensis venom) have been studied by reducing both the proteins by treatment with reduced dithiothreitol followed by renaturation by treatment with oxidised dithiothreitol. isoelectric focusing of the samples trapped at varying time intervals during renaturation of the proteins reveals formation of intermediates in the folding pathway with cardiotoxin 3.10.2. having fewer intermediates than erabutoxin b ... | 1994 | 8076968 |
| effects of different antagonists on depolarization of cultured chick myotubes by cobra venom cardiotoxins and pyrularia thionin from the plant pyrularia pubera. | cardiotoxins (3.12 and 3.12.1) purified from cobra venom (naja naja siamensis) are basic single-chain polypeptides of about 60 residues. although they depolarize nerve and muscle cells and have cytolytic effects, their mechanism of action is still unknown. pyrularia thionin (p-thionin) isolated from nuts of the parasitic plant pyrularia pubera is a strongly basic, single-chain polypeptide containing 47 residues. it is known to be haemolytic and cytotoxic, and to depolarize muscle cells, but its ... | 1993 | 8303717 |
| effect of polar head groups on the interactions of phospholipase a2 with phosphonate transition-state analogues. | several new phosphonate-containing phospholipid analogues were synthesized as inhibitors of cobra venom (naja naja naja) phospholipase a2. these phospholipid analogues contained a novel thioether at the sn-1 position, a tetrahedral phosphonate moiety in place of the scissile ester bond at the sn-2 position, and several different polar head groups, including phosphocholine, phospho(n,n-dimethylethanolamine), phospho(n-methylethanolamine), and phosphoethanolamine. the affinities of these analogues ... | 1993 | 8399145 |
| interaction of phospholipase a2 with thioether amide containing phospholipid analogues. | transferred noe experiments have been carried out on cobra venom (naja naja naja) phospholipase a2 (pla2) with substrate analogues which serve as potent inhibitors. 1-(hexylthio)-2-(hexanoylamino)-1,2-dideoxy-sn-glycero-3-pho sphoethanolamine (pe) and the corresponding phosphocholine analogue (pc) are water-soluble, short-chain, nonhydrolyzable substrate analogues which bind tightly to the enzyme. because they are small compounds and monomeric in solution, noes develop inefficiently in the absen ... | 1993 | 8494876 |
| two-dimensional 1h-nmr study of the spatial structure of neurotoxin ii from naja naja oxiana. | the spatial structure of neurotoxin ii from the venom of the central asian cobra naja naja oxiana was determined by two-dimensional 1h-nmr techniques and computational analysis. nearly complete proton resonance assignments for 61 amino acid residues have been made using two-dimensional (2d) homonuclear total correlated spectroscopy, 2d homonuclear double-quantum-filtered correlated spectroscopy and 2d homonuclear noe spectroscopy (noesy) experiments. the cross-peak volumes in noesy spectra spin- ... | 1993 | 8504813 |
| three-dimensional structure of neurotoxin-1 from naja naja oxiana venom at 1.9 a resolution. | neurotoxin-1 from naja naja oxiana venom (ntx-1) has been crystallized by vapor diffusion in sitting drops. the crystals have cell dimensions of a = 25.2 a, b = 75.6 a, c = 35.9 a, and are in space group p2(1)2(1)2(1). three-dimensional data to 1.9 a have been recorded by a syntex p2(1) automatic diffractometer. the atomic structure of the toxin has been determined by molecular replacement using the alpha-cobratoxin (alpha-ctx) as the search model. the position of 534 non-hydrogen protein atoms ... | 1993 | 8458425 |
| mapping the functional topography of a receptor. | photoactivatable derivatives of the alpha-neurotoxin ii from naja naja oxiana are useful tools for investigating the three dimensional architecture of the extra-membrane part of the nicotinic acetylcholine receptor from the electric tissue of torpedo californica. three derivatives, carrying an azidobenzoyl group in position lys-15, lys-26, and lys-46, respectively, are shown to react differently within the receptor's quaternary structure. especially the lys-26 and lys-46 derivatives can be used ... | 2007 | 1299215 |
| comparative characterization of two toxic phospholipases a2 from indian cobra (naja naja naja) venom. | indian cobra venom contains many phospholipase a2 (pla2) toxins. in the present study two toxic pla2s have been purified from the indian cobra (naja naja naja) venom by column chromatography. the nn-xia-and nn-xib-pla2s have mol. wts between 10,700 and 15,000. the nn-xia-pla2 induces myotoxic effects, oedema and neurotoxicity in mice and has an i.p. ld50 of 8.5 mg/kg body weight. the nn-xia-pla2 is also cytotoxic to ehrlich ascites tumour cells. the other pla2, nn-xib, in contrast has an i.p. ld ... | 1992 | 1279838 |
| alpha-cobratoxin: proton nmr assignments and solution structure. | the solution structure of alpha-cobratoxin, a neurotoxin purified from the venom of the snake naja naja siamensis, at ph 3.2 is reported. sequence-specific assignments of the nmr resonances was attained by a combination of a generalized main-chain-directed strategy and of the sequential method. the nmr data show the presence of a triple-stranded beta-sheet (residues 19-25, 36-41, and 52-57), a short helix, and turns. an extensive number of noe cross peaks were identified in the noesy nmr maps. t ... | 1992 | 1317211 |
| isolation and characterization of a lethal phospholipase a2 (nn-ivb1-pla2) from the indian cobra (naja naja naja) venom. | indian cobra (naja naja naja) venom is reported to contain multiple forms of phospholipase a2. only a couple of them have been isolated and characterized. a lethal phospholipase a2 (nn-ivb1-pla2) from naja naja naja venom has been purified in three steps involving cm-sephadex c-25, sephadex g-50 and rechromatography on cm-sephadex c-25 columns. it is a basic protein with pl value between 7-7.5 and has molecular weight between 11,000-11,500. the ld50 of nn-ivb1-pla2 is 1.2 mg/k g body weight. it ... | 1991 | 1810247 |
| the refined crystal structure of alpha-cobratoxin from naja naja siamensis at 2.4-a resolution. | the crystal structure of the "long" alpha-neurotoxin alpha-cobratoxin was refined to an r-factor of 19.5% using 3271 x-ray data to 2.4-a resolution. the polypeptide chain forms three loops, i, ii, iii, knotted together by four disulfide bridges, with the most prominent, loop ii, containing another disulfide close to its lower tip. loop i is stabilized by one beta-turn and two beta-sheet hydrogen bonds; loop ii by eight beta-sheet hydrogen bonds, with the tip folded into two distorted right-hande ... | 1991 | 1939183 |
| critical role of a hydrogen bond in the interaction of phospholipase a2 with transition-state and substrate analogues. | the inhibition of phospholipase a2 by an amide substrate analogue, 1-hexadecylthio-2-hexadecanoyl-amino-1,2-dideoxy-sn-glycero-3-phos phocholine, and a phosphonate transition-state analogue, 1-hexadecylthio-1-deoxy-2-hexadecylphosphono-sn-glycero-3-ph osphocholine, is dramatically influenced by ph. however, these two inhibitors show opposite ph dependencies. the amide analogue acts more potently under basic conditions, whereas the phosphonate acts more potently under acidic conditions. in both c ... | 1991 | 1924395 |
| synthesis and characterization of a heterobifunctional mercurial cross-linking agent: incorporation into cobratoxin and interaction with the nicotinic acetylcholine receptor. | the heterobifunctional organomercurial reagents 3-(acetoxymercurio)- and 3-(chloromercurio)-5-nitrosalicylaldehyde were prepared, characterized in model studies, and used to probe the interaction between cobratoxin, purified from the venom of the thailand cobra (naja naja siamensis), and the affinity-purified nicotinic acetylcholine receptor (acchr) from torpedo california electroplax. these reagents may also be useful in introducing chemically well-defined heavy metal atoms into proteins contai ... | 1991 | 1854732 |
| anionic subsites of the catalytic center of acetylcholinesterase from torpedo and from cobra venom. | a peptide of acetylcholinesterase (acchoease; acetylcholine acetylhydrolase, ec 3.1.1.7) from the venom of the cobra naja naja oxiana labeled by the affinity reagent n,n-dimethyl-2-phenylaziridinium (dpa) has been identified. the sequence is gly-ala-glu-met-trp-asn-pro-asn. in acchoease from torpedo californica, a homologous peptide was labeled and isolated. its sequence is ser-gly-ser-glu-met-trp-asn-pro-asn, representing positions 79 through 87. in both cases labeling can be prevented by 0.1 m ... | 1991 | 2068091 |
| extensive multiplicity of the miscellaneous type of neurotoxins from the venom of the cobra naja naja naja and structural characterization of major components. | a multiplicity of miscellaneous type neurotoxins were detected in the venom of the cobra naja naja naja by use of reverse-phase hplc and fplc. the primary structures of major forms were determined, giving 4 novel structures. all four contain 62-65 residues, with 10 half-cystine residues and resemble the miscellaneous type of toxins from other naja species. differences within the species are extensive, exchanges occur at 27 positions, giving only 58% residue identity between all forms. however, t ... | 1991 | 2060629 |
| [spatial structure of the basic chain of the neurotoxin i molecule from the venom of cobra naja naja oxiana and its crystal packing]. | the structure of the alpha-carbon chain was solved by molecular replacement method at 2.7 a resolution. neurotoxin i (ntx-i) is one of the main protein components purified from the venom of the central asian cobra naja naja oxiana. ntx-i is known to bind specifically to acetylcholine receptors thus preventing the transmission of the neuroconductivity signal from synapses to muscles. ntx-i crystals were grown either by vapour diffusion or dialysis methods using specially prepared microdialysis ce ... | 1991 | 2064629 |
| cobra venom phospholipase a2: naja naja naja. | | 1991 | 2051932 |
| purification and characterization of a neurotoxic phospholipase a2 from indian cobra (naja naja naja) venom. | snake venoms contain multimolecular forms of phospholipase a2 which are diverse with respect to their pharmacological properties. a neurotoxic pla2 from naja naja naja venom has been purified in two steps. (1) the whole venom was fractionated on cm-sephadex c-25 column; 4.6% of the total pla2 activity recovered was found in the nn-v fraction. (2) the nn-vb-pla2 fraction was purified to homogeneity by gel filtration of fraction nn-v on sephadex g-50. it is a basic protein with a mol. wt between 1 ... | 1991 | 1814010 |
| purification and characterization of a chymotrypsin kunitz inhibitor type of polypeptide from the venom of cobra (naja naja naja). | a chymotrypsin kunitz inhibitor type of polypeptide has been isolated from the venom of naja naja naja by reverse phase hplc and cation exchange fplc. it is present in a considerably lower amount than that of the corresponding trypsin inhibitor. the primary structure, determined by sequence analysis of the whole molecule and its tryptic peptides, has 57 residues with an apparent molecular mass of 6.2 kda. the main contact site with the protease (p1) has a phe, showing the specificity of the inhi ... | 1990 | 2262001 |
| crystallization and preliminary x-ray diffraction study of neurotoxin-i from naja naja oxiana venom. | crystals of the neurotoxin-i (ntx-i) from the venom of the middle asian cobra naja naja oxiana have been grown by vapour diffusion and dialysis methods. the crystals belong to space group p2(1)2(1)2 with dimension of a = 25.19 a, b = 75.59 a, c = 36.09 a and diffract to 1.9 a resolution. the asymmetric unit contains one molecule (vm = 2.2 a/da). using the molecule of alpha-cobratoxin (ctx) as a starting model for ntx-i structure determination coordinates of c alpha atoms of the ntx-i molecule we ... | 1990 | 2387409 |
| orientation of cobra alpha-toxin on the nicotinic acetylcholine receptor. fluorescence studies. | four flourescein isothiocyanate (fitc) derivatives of naja naja siamemsis 3 neurotoxin (alpha-toxin), labeled at the epsilon-amino groups of lys-23, lys-35, lys-49, or lys-69, and a tetramethylrhodamine isothiocyanate (tritc) derivative, labeled at epsilon-amino group of lys-23, were prepared and used to analyze the orientation of cobra alpha-toxin on the nicotinic acetylcholine receptor (acchr) relative to both the plane of the membrane and the central ion channel. fluorescence-quenching studie ... | 1990 | 2110165 |
| characterization of a cytotoxin-like basic protein from the cobra (naja naja naja) venom. | a cytotoxin-like basic protein has been isolated from the venom of the nominate race of cobra (naja naja naja from pakistan) by a single step of high-performance liquid chromatography. the primary structure was determined and consists of 62 amino acid residues in a single polypeptide chain. it is highly similar to that of the cytotoxin-like basic proteins isolated from other naja species, but differs in two of the ss-loop structures from that of cytotoxins. | 1990 | 2311757 |
| the interaction of phospholipase a2 with phospholipid analogues and inhibitors. | a series of structurally modified phospholipids have been used to delineate the structural features involved in the interaction between cobra venom (naja naja naja) phospholipase a2 and its substrate. special emphasis has been placed on sn-2 amide analogues of the phospholipids. these studies have led to a very potent, reversible phospholipase a2 inhibitor. a six-step synthesis of this compound, 1-palmitylthio-2-palmitoylamino-1,2-dideoxy-sn-glycero-3- phosphorylethanolamine (thioether amide-pe) ... | 1990 | 2303420 |
| nonequivalence of alpha-bungarotoxin binding sites in the native nicotinic receptor molecule. | in the native, membrane-bound form of the nicotinic acetylcholine receptor (m-acchr) the two sites for the cholinergic antagonist alpha-bungarotoxin (alpha-bgt) have different binding properties. one site has high affinity, and the m-acchr/alpha-bgt complexes thus formed dissociate very slowly, similar to the complexes formed with detergent-solubilized acchr (s-acchr). the second site has much lower affinity (kd approximately 59 +/- 35 nm) and forms quickly reversible complexes. the nondenaturin ... | 1990 | 2340276 |
| amino acid sequence and circular dichroism of indian cobra (naja naja naja) venom acidic phospholipase a2. | the full amino acid sequence of the acidic phospholipase a2 from indian cobra (naja naja naja) venom was determined and its tertiary structure examined by circular dichroism (cd). the sequence was aligned with other sequences of secreted phospholipase a2 from snakes of the genus naja, using the progressive alignment method of feng and doolittle (j. mol. evol. (1987) 25, 351-360). the primary sequence of naja naja naja phospholipases a2 shows up to 85% identity with the other acidic naja phosphol ... | 1990 | 2294972 |
| pattern of acetylcholinesterase activity in the hypothalamus of the cobra, naja naja. | application of acetylcholinesterase (ache) method to the hypothalamus of the cobra naja naja revealed a clearly discernible pattern of activity in the nuclear groups. the magnocellular neurons distributed in various subdivisions showed strong reaction. among the parvocellular groups, intense enzyme activity was observed in the cells of nucleus subfornicalis, nucleus hypothalamicus medialis, dorsal and ventral subdivisions of the nucleus hypothalamicus lateralis and the nucleus mamillaris. the pa ... | 1990 | 2358653 |
| effect of modification of tyrosine residues in cytotoxin-1 from indian cobra venom. (naja naja naja). | the role of tyrosine residues in the biological activity of cytotoxin-1 was evaluated using n-bromo succinimide. n-bromo succinimide effected the oxidation of tyrosine residues in cytotoxin-1 with an increase in absorption at 260 nm. n-chloro succinimide was ineffective in the oxidation of tyrosine residues in the toxin. oxidation of a single tyrosine residue (at 3.50 equivalents of n-bromo succinimide/mole of the toxin) resulted in complete loss of lethal activity of the toxin. the lytic activi ... | 1990 | 2350359 |
| ablation of natural killer cell function by soluble cardiotoxin. | a one-hour preincubation of nonadherent murine spleen cells with a soluble membrane-active cardiotoxin purified from the venom of the thailand cobra naja naja siamensis results in the destruction of natural killer (nk) cell activity against yac-1 target cells in a dose-dependent manner. prior in vivo induction of interferon production by polyinosinic/polycytidylic acid does not avert the cardiotoxin inhibition of nk function. loss of complement-mediated lysis of cells capable of binding an nk-1. ... | 1990 | 2329017 |
| [comparison of two elapidae venoms: naja naja and naja nigricollis]. | in our study on the identification of snake venoms by electrofocusing technics, the protein profiles of naja naja naja, naja nigricollis pallida and naja nigricollis west africa were compared. the typical profile of venoms of elapidae was easily identified in this comparison. the two species could easily be differentiated, whereas the differences between the two sub-species were more difficult to evidence, since they are geographic variants of the same type. | 1990 | 2291604 |
| in vivo interactions between neurotoxin, cardiotoxin and phospholipases a2 isolated from malayan cobra (naja naja sputatrix) venom. | the in vivo interactions between alpha-neurotoxin, cardiotoxin and two phospholipases a2 (sputa-phospholipase a2-1 and 3) isolated from malayan cobra venom were assessed by examining the effects of simultaneous injection of sub-ld50 dose of one toxin on (i) i.v. ld50 s of the other toxins in mice; and (ii) mean survival times of mice injected with lethal doses of the other toxins. while ld50 measurements did not reveal any interaction between the toxins in vivo, survival time measurements sugges ... | 1990 | 2264068 |
| phospholipase a2 from cobra (naja naja naja) venom. primary structure and subspecies variation. | the primary structure of phospholipase a2 of the major race of indian cobra has been determined. together with previous data on other subforms, it establishes subspecies variations at no less than 20 of the 119 positions in the protein. these variations are large, not only in number but in several cases also regarding properties of the residues involved. nevertheless, all structures are compatible with largely unaltered enzyme properties. | 1989 | 2626425 |
| the anticoagulant activity of malayan cobra (naja naja sputatrix) venom and venom phospholipase a2 enzymes. | malayan cobra (naja naja sputatrix) venom was found to exhibit an in vitro anticoagulant activity that was much stronger than most common cobra (genus naja) venoms. the most potent anticoagulants of the venom are two lethal phospholipase a2 enzymes with pi's of 6.15 and 6.20, respectively. the anticoagulant activity of the venom is due to the synergistic effect of the venom phospholipase a2 enzymes and polypeptide anticoagulants. bromophenacylation of the two phospholipase a2 enzymes reduced the ... | 1989 | 2619749 |
| interaction of central asian cobra (naja naja oxiana eichwald) venom cytotoxins with phospholipase d. | effect of cytotoxins from the venom of naja naja oxiana eichwald on the hydrolytic function of phospholipase d has been further analysed. cytotoxins in the absence of ca2+ activated the enzyme, whereas in its presence they inhibited it. inhibition is shown to be related to the interaction of cytotoxins with the enzyme which blocks the absorption of the enzyme at the surface of the substrate phase. synergism in the action of cytotoxin and phospholipase d was not noticed. | 1989 | 2628264 |
| comparison of tensilon and antivenom for the treatment of cobra-bite paralysis. | we prospectively compared the ability of anti-venom and edrophonium (tensilon) to improve paralytic symptoms in 8 patients envenomed by the philippine cobra (naja naja philippinensis). twenty, 50 or 100 ml of philippine cobra antivenom were administered in a double-blind fashion by constant intravenous infusion over 30 min. even the largest dose of antivenom failed to produce marked improvement within 2 h, though enzyme-linked immunosorbent assays and neutralization tests demonstrated that it po ... | 2013 | 2694492 |
| isolation and characterization of an acidic lethal phospholipase az from malayan cobra (naja naja sputatrix) venom. | an acidic, lethal phospholipase az was purified to electrophoretic homogeneity from the venom of the malayan cobra (naja naja sputatrix). the enzyme has an isoelectric point of 5.58, a molecular weight of 12000, and a medium lethal dose (ld50) of 0.86 micrograms/g in mice by intravenous injection. the enzyme also exhibited weak anticoagulant and edema-forming activities. the amino acid composition of the enzyme is similar to those of other cobra venom phospholipases az. | 1989 | 2764979 |
| induction of alveolar epithelial injury by phospholipase a2. | severe damage to the alveolar type i epithelial cell is a characteristic morphological feature of lung injury due to numerous cases. it is postulated that excess phospholipase a2 (pla2) activity might be responsible for these changes, as one of the naturally occurring products of this enzyme, lysophosphatidylcholine (lysopc) has been shown to cause selective injury to the type i pneumonocyte when it is instilled into the lower air spaces of the lung. to further investigate this potential mechani ... | 1989 | 2917929 |
| oral toxicity of central asian cobra (naja naja oxiana eichwald) venom and its fractions to adult blowflies parasarcophaga ruficornis fabricius. | | 1988 | 3248836 |
| bites by the philippine cobra (naja naja philippinensis): prominent neurotoxicity with minimal local signs. | we studied 39 patients envenomed by the philippine cobra (naja naja philippinensis). neurotoxicity occurred in 38 cases and was the predominant clinical feature. respiratory paralysis developed in 19 patients, and was often rapid in onset--in 3 cases apnea occurred within 30 min of the bite. there were 2 deaths, both in patients who were moribund upon arrival at the hospital. three patients developed necrosis, and 14 individuals with systemic symptoms had no local swelling. both cardiotoxicity a ... | 1988 | 3177741 |
| higher order structure of chloroplastic 5s ribosomal rna from spinach. | the secondary and tertiary structure of chloroplastic 5s ribosomal rna from spinach was investigated by the use of several chemical and enzymatic structure probes. the four bases were monitored at one of their watson-crick base-pairing positions with dimethyl sulfate [at a(n1) and c(n3)] and with 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate [at g(n1) and u(n3)]. position n7 of purines was probed with diethyl pyrocarbonate (adenines) and with dimethyl sulfate (guanines) ... | 1988 | 3167011 |
| amino-acid sequences of four cytotoxins (cytotoxins i, ii, iii and iv) purified from the venom of the thailand cobra, naja naja siamensis. | four cytotoxins, designated as cytotoxins i, ii, iii and iv, were isolated from the venom of the thailand cobra (naja naja siamensis) by gel filtration on sephadex g-75 followed by cm-cellulose chromatography. the amino-acid sequences were determined by a combination of conventional methods. cytotoxins i, ii, iii and iv were each composed of 60 amino-acid residues and their molecular weights were calculated to be 6693, 6646, 6709 and 6739, respectively. the amino-acid sequences were compared wit ... | 1988 | 3365434 |
| a role for acetylcholine receptors in the fusion of chick myoblasts. | the role of acetylcholine receptors in the control of chick myoblast fusion in culture has been explored. spontaneous fusion of myoblasts was inhibited by the nicotinic acetylcholine receptor antagonists alpha-bungarotoxin, naja naja toxin and monoclonal antibody mcab 5.5. the muscarinic antagonists qnb and n-methyl scopolamine were without effect. atropine had no effect below 1 microm, where it blocks muscarinic receptors; at higher concentrations, when it blocks nicotinic receptors also, atrop ... | 1988 | 3372592 |
| tourniquet application after cobra bite: delay in the onset of neurotoxicity and the dangers of sudden release. | the effects of tourniquet application were prospectively studied in 36 hospitalized patients who developed neurotoxic symptoms after bites by the philippine cobra (naja naja philippinensis). tourniquets had been applied in 94% of cases and delayed the onset of symptoms. four patients were asymptomatic prior to the release of their tourniquet and in 11 patients symptoms worsened precipitously. most importantly, 4 patients developed complete respiratory paralysis requiring artificial ventilation o ... | 1988 | 3275141 |
| purification and characterization of four monofluorescein cobra alpha-toxin derivatives. | we labeled cobra-alpha-toxin (naja naja siamensis 3) with near stoichiometric quantities of fluorescein isothiocyanate. to reduce labeling of the hyperreactive n epsilon-lysine 23, the alpha-toxin was modified reversibly with citraconic anhydride before fluorescein labeling. the citraconic anhydride was later removed with strong acid, and four of the six possible monofluorescein alpha-toxin derivatives were isolated by isoelectric focusing on an immobilized ph gradient. thermolysin digestion and ... | 1988 | 3125169 |
| effect of phospholipids on fluorescence polarization and lifetimes of fluorescein-labeled phospholipase a2. | phospholipids and divalent metal ions induce changes in the fluorescence polarization of fluorescein-labeled phospholipase a2 from the indian cobra (hazlett, t.l. and dennis, e.a. (1985) biochemistry 24, 6152-6158) which may be indicative of enzyme aggregation. lifetimes and rotational correlation times of the conjugate in the presence of these and other ligands are now reported. the correlation times of monomeric phospholipase a2 were shorter than expected for a hydrated, 13,000 molecular weigh ... | 1988 | 3337833 |
| toxicity of central asian cobra (naja naja eichwald) venom and its components to the larvae of blowfly parasarcophaga ruficornis fabr. | | 1988 | 3397115 |
| a comparative study of cobra (naja) venom enzymes. | 1. the l-amino acid oxidase, hyaluronidase, alkaline phosphomonoesterase, protease, phosphodiesterase, acetylcholinesterase, phospholipase a and 5'-nucleotidase activities of 47 samples of venoms from all the six species of cobra (naja), including five subspecies of naja naja, were examined. 2. the results demonstrated interspecific differences in the venom contents of phospholipase a, acetylcholinesterase, hyaluronidase and phosphodiesterase. these differences in venom enzyme contents can be us ... | 1988 | 2854766 |
| the binding site for alpha-bungarotoxin resides in the sequence 188-201 of the alpha-subunit of acetylcholine receptor: structure, conformation and binding characteristics of peptide [lys] 188-201. | in order to study where the binding site of cholinergic agents is in the sequence of the alpha-subunit of nicotinic acetylcholine receptor (achr), we have synthetized 3 peptides with an amino acid sequence corresponding to the following sequences of the alpha-subunit of torpedo californica achr: 125-143, 158-167, [lys] 188-201. for binding studies the peptides were immobilized on sepharose 4b. only the peptide [lys] 188-201 binds 125i-alpha-bungarotoxin (alpha-bgtx) with kd of 1.03 microm. the b ... | 1987 | 3696481 |
| bites by the philippine cobra (naja naja philippinensis): an important cause of death among rice farmers. | we investigated mortality from cobra (naja naja philippinensis) bite among filipino rice farmers. village records in one area were examined and we conducted a careful survey in this and two additional areas among inhabitants at varying risk for snakebite. the death rate from cobra bite was estimated to be as high as 107.1 deaths per 100,000 population per year at one site. most victims were young (median age 17) and 98% were males. only 8% of the victims studied reached a hospital. the confirmed ... | 1987 | 3688317 |
| partial sequence of hemoglobin from cobra (naja naja naja). | hemoglobin from the cobra snake, naja naja naja, was isolated and its chains separated on a cm-cellulose column. the separation profile revealed an alpha and two beta chains having the molar proportions of [alpha]2[beta 1]1[beta 2]1. the n-terminal amino acid sequence of the intact chains and of the cnbr peptides were carried out. the beta 2 chain was found to be heterogeneous comprising a minor component amounting to 11%. this later showed changes at two positions 9 and 14 in the first 30 resid ... | 1987 | 3447643 |
| amino acid sequence of a cytotoxin-like basic protein with low cytotoxic activity from the venom of the thailand cobra naja naja siamensis. | a cytotoxin-like basic protein (clbp) was isolated from the venom of the thailand cobra (naja naja siamensis). the cytotoxicity of clbp toward fl cells was one order of magnitude lower than those of cytotoxins. the amino acid sequence was determined by a combination of conventional methods. the total number of amino acid residues was 62, giving a molecular mass of 6977 da. the sequence at residues 25-30 in the clbp molecule was found to be significantly different from those of cytotoxins. this r ... | 1987 | 3595859 |
| a new ribonuclease from cobra venom (naja naja) showing specificity towards cytidylic acid. | a ribonuclease was isolated and purified to homogeneity from cobra venom. the enzyme was found to be homogeneous on sds and non-sds polyacrylamide gel electrophoreses, and high performance liquid chromatography. the purified enzyme hydrolysed poly(rc), but not poly(ra), poly(ru), poly(rg), poly(ri), or poly(ri).poly(rc). the presence of magnesium was found to be an essential requirement for the nucleolytic activity of this enzyme. | 1987 | 3593367 |
| a one-step isolation procedure for phospholipase a2-free cobra venom factor by fast protein liquid chromatography. | a very rapid and efficient procedure for isolation of cobra venom factor (cof) from naja naja venom is presented. the method is based on mono q anion exchange chromatography on a system for fast protein liquid chromatography (fplc). cof was eluted by a buffer of ph 7.4 at 280 mm salt. a purification of 33.7 x was reached with a yield of at least 27%. contamination with phospholipase was under the detection limit of a sensitive radiometric assay (less than 25 ppm), while the starting material con ... | 1987 | 3819435 |
| effects of cardiotoxin d from naja naja siamensis snake venom upon murine splenic lymphocytes. | cardiotoxin d from naja naja siamensis is cytotoxic to t-lymphocytes above 150 femtomoles/10(6) cells. equivalent lysis of macrophages or b-lymphocytes requires at least 1000 times more toxin. reduction and carboxamidomethylation of cardiotoxin d does not effect t cell lysis. at higher toxin concentrations, 50% t-cell lysis occurs within 10 min. splenocytes cultured with mitogens are up to five times more susceptible to toxin than unstimulated cells. cardiotoxin d may directly disrupt the plasma ... | 1987 | 3433298 |
| positive response to edrophonium in patients with neurotoxic envenoming by cobras (naja naja philippinensis). a placebo-controlled study. | to study the ability of anticholinesterase drugs to reverse the potentially fatal paralytic effects of cobra venom, we conducted a placebo-controlled, double-blind crossover trial of intravenous edrophonium (tensilon) in 10 adults with neurotoxic envenoming caused by bites of the philippine cobra (naja naja philippinensis). there was significantly more improvement in ptosis and endurance of upward gaze after edrophonium than after placebo. five minutes after injection, the mean difference (+/- s ... | 1986 | 3537783 |
| selectivity and regulation in the phospholipase a2-mediated attack on cholinergic synaptic vesicles by beta-bungarotoxin. | the total fatty acid composition of purified torpedo californica electric organ synaptic vesicles was determined by glc analysis of methyl esters. limit amounts of fatty acids released by high concentrations of either beta-bungarotoxin (beta-butx) or naja naja venom phospholipase a2 (pla2) acting in deoxycholate are reported. the time and enzyme concentration dependence for beta-butx- and pla2-induced release of fatty acids from intact synaptic vesicles indicate that pla2 is 100- to 1,000-fold m ... | 1986 | 3746303 |
| rate-determining step in phospholipase a2 mechanism. 18o isotope exchange determined by 13c nmr. | h2(18)o isotope exchange into specifically 13c-labeled substrate was used to obtain information on the rate-limiting step in the action of the phospholipase a2 from the venom of the indian cobra (naja naja naja). incorporation of 18o was detected by the effect of 18o on 13c chemical shifts in 13c nmr. the enzymatic hydrolysis of a micellar phosphatidylcholine analogue of platelet-activating factor 1-alkyl-2-[1-13c]lauroyl-sn-glycero-3-phosphorylcholine proceeds by an o-acyl cleavage of the sn-2 ... | 1986 | 3745162 |
| 1-stearyl,2-stearoylaminodeoxy phosphatidylcholine, a potent reversible inhibitor of phospholipase a2. | 1-stearyl, 2-stearoylaminodeoxy phosphatidylcholine, a structurally modified phospholipid substrate analog exhibits potent and reversible inhibition of phospholipase a2 from cobra venom (n. naja naja). the apparent ki values determined in two different assay systems employing phosphatidylcholine-surfactant mixed micelles are in reasonable agreement (40 microm and 16 microm) and indicate that the inhibitor binds to the enzyme as much as two orders of magnitude more tightly than does dipalmitoyl p ... | 1986 | 3755338 |
| analysis of folding intermediates from the main toxin of naja naja samarensis containing two blocked cysteines. | the formation of folding intermediates blocked by iodoacetate from the main toxin of naja naja samarensis was monitored by fplc and the populations were identified by amino acid analyses. we have determined conditions allowing for the highest yield in the populations with two blocked cysteines. the free cysteines remaining under these conditions were labeled with iodo[14c]acetate and localized by peptide mapping in one of the products isolated by ion-exchange chromatography (nt3iii). we have als ... | 1986 | 3699158 |
| [effect of modification of naja naja oxiana neurotoxin ii on the stoichiometry of its complexes with acetylcholine receptor]. | it was discovered that illumination of the complex formed by the solubilized acetylcholine receptor from torpedo marmorata and lys25-p-azidobenzoyl derivative of neurotoxin ii results in the appearance on the receptor of up to 4 additional binding sites. acetylcholine and neurotoxin ii, but not the long-chain neurotoxins bind specifically to these sites. the additional binding sites could be also detected after illuminating the receptor complex with other photoactivable derivatives, provided the ... | 1986 | 3718547 |
| [synthesis of tritium-labeled n,n-dimethyl-2-phenylaziridinium and its reaction with acetylcholinesterase]. | the synthesis of tritium-labeled n,n-demethyl-2-phenylaziridinium has been described. the specific radioactivity of the product obtained was 1,06 tbq/mmole. kinetics of incorporation of this radioactive label into acetylcholinesterase of cobra venom (naja naja oxiana) has been studied at 1,05 mm ligand concentration (25 degrees c, ph 7,50. 0,15 m phosphate buffer). under these conditions two molecules of the radioactive label have been found to react with the enzyme. one molecule incorporates fa ... | 1985 | 4074397 |
| binding of a curarimimetic toxin from cobra venom to the nicotinic acetylcholine receptor. interactions of six biotinyltoxin derivatives with receptor and avidin. | we have reacted n-hydroxysuccinimidyl biotin with the principal curarimimetic toxin in naja naja siamensis venom, biotinylating each of the five lysine residues and the n-terminal isoleucine. the six monobiotinyl-toxins were isolated by ion-exchange chromatography, and the residue modified in each was identified by peptide mapping and amino acid analysis. we evaluated the role of each lysine in the binding of toxin to the acetylcholine receptor by measuring the affinity of each biotinyltoxin for ... | 1985 | 3161881 |
| action of cobra venom phospholipase a2 on large unilamellar vesicles: comparison with small unilamellar vesicles and multibilayers. | phospholipase a2 (naja naja naja) catalyzes the hydrolysis of dipalmitoyl phosphatidylcholine in small unilamellar vesicles (suvs) with a faster initial rate than in large unilamellar vesicles (luvs) and multilamellar vesicles (mlvs). for the suvs, the hydrolysis was initially faster for gel phase than liquid crystalline phase phospholipid. for both luvs and mlvs, hydrolysis was low except in a small temperature range around the thermotropic phase transition of the phospholipid. in this temperat ... | 1985 | 3838567 |
| affinity chromatography of phospholipase a2 from naja naja naja (indian cobra) venom. | a rapid and improved purification procedure is described for phospholipase a2 from the indian cobra, naja naja naja. the procedure is based on affinity chromatography of the venom through affi-gel blue to obtain a 9-fold purification in one step. however, as there are multiple forms of the enzyme in the venom and other proteins do bind to affi-gel blue, further purification is achieved by de-11 cellulose. finally, a minor contaminant is removed by sulfopropyl sephadex c-25 chromatography. the re ... | 1985 | 3927524 |
| adrenergic receptors of isolated snake atria. | cardiac adrenergic receptors in snakes were examined using an isolated atria preparation of naja naja and ptyas korros. treatments included an examination of the atrial responses to selective alpha- and beta-adrenergic agonists and antagonists. in both species, both phenylephrine and isoproterenol produced dose-dependent increases in the atrial beating rate and tension. phenylephrine-induced increases were characterized with a high affinity and low affinity components. these positive chronotropi ... | 1985 | 2861969 |
| reoxidation and renaturation studies on the main toxin of naja naja samarensis. | the main toxin of naja naja samarensis is a very small and rigid protein (mr 6850, 8 cysteines). when fully reduced, it regains its native conformation by a mechanism involving a rapid cysteine oxidation and a slower, less temperature-dependent disulfide exchange. in a native-like form of the protein we observed a population whose cysteines were incompletely reoxidized. when intermediates with blocked cysteines were incubated with oxidized and reduced glutathione, the percentage of native-like m ... | 1984 | 6500055 |
| [2-d-nmr study of the conformation characteristics of toxin 3 from naja naja siamensis venom]. | the spatial structure of "long" toxin 3 naja naja siamensis in solution has been studied by methods of two-dimensional (2d) 1h nmr spectroscopy. the individual signal assignments for 67 out of 71 residues and analysis of nuclear overhauser effects between distinct protons of the molecule allowed the comparison of the toxin 3 conformations at different ph values and temperatures. it was shown that the deprotonated imidazole ring of his22 residue (at ph greater than or equal to 7,5) is surrounded ... | 1984 | 6529443 |
| amino acid sequence of cytotoxin iia isolated from the venom of the indian cobra (naja naja). | a cytotoxic basic polypeptide, designated as cytotoxin iia, was purified to homogeneous state from the venom of the indian cobra (naja naja) by a combination of gel filtration on sephadex g-50, cm-cellulose chromatography, and fast protein liquid chromatography. cytotoxin iia is a single polypeptide consisting of 60 amino acid residues with four intramolecular disulfide linkages. the toxin showed high cytotoxicity toward yoshida sarcoma and ascites hepatoma cells as did cytotoxins i and ii isola ... | 1984 | 6525197 |
| [nmr study of the spatial structure of the naja naja siamensis toxin 3]. | the 300 and 500 mhz 1h nmr spectra of a long-chain neurotoxin, toxin 3 naja naja siamensis (s-t3), its derivatives and close homolog, toxin 3 naja naja naja (n-t3), have been analyzed. a combination of double resonance, difference spectroscopy and usage of a series of toxin s-t3 derivatives acetylated or trifluoroacetylated at lysine residues allowed to assign the signals from all aromatic protons and a number of signals in the aliphatic region, and to elucidate the microenvironment of certain f ... | 1984 | 6437411 |
| fluorescence energy transfer between cobra alpha-toxin molecules bound to the acetylcholine receptor. | an approach was developed with steady state fluorescence energy transfer measurements to examine the spatial relationship between the two alpha-toxins bound to the acetylcholine receptor. by taking advantage of the slow dissociation rates of alpha-toxins (naja naja siamensis 3) from the receptor and of the equal probability with which alpha-toxins bind to the two alpha-toxin-binding sites, we derived an equation which allows prediction of a "true" efficiency of transfer based on the relationship ... | 1984 | 6715368 |
| effect of central asian cobra (naja naja oxiana eichwald) venom cytotoxin on enzymatic hydrolysis of phospholipids. | | 1984 | 6490078 |
| [relative localization of the bound acetylcholine receptor subunits and neurotoxin]. | a series of neurotoxin ii (naja naja oxiana) derivatives, each containing one p-azido-[14c]benzoyl group, have been prepared. those labeled at leu1, lys15, lys25, lys26, or lys46 associate specifically with the acetylcholine receptor from the torpedo marmorata electric organs and form the crosslinks with it as a result of irradiation. electrophoresis in polyacrylamide gel and gel chromatography revealed the contacts between the neurotoxins and alpha, beta, gamma and delta subunits of the recepto ... | 1984 | 6487390 |
| a comparison of eel electroplax and snake venom acetylcholinesterase. | the effects of some cholinergic ligands, harmala alkaloids and local anesthetics on the activity of eel electroplax and naja naja siamensis venom acetylcholinesterase have been studied. in most cases, eel electroplax was found to be more susceptible towards inhibition than the venom acetylcholinesterase. no major difference was observed with respect to the type of inhibition in both enzymes. the activation of the two enzyme preparations by inorganic cations (ca2+, mg2+ and na+) showed a similar ... | 1984 | 6146473 |
| purification of acidic phospholipases from indian cobra (naja naja naja) venom. | | 1983 | 6668341 |
| chiral synthesis of a dithiolester analog of phosphatidylcholine as a substrate for the assay of phospholipase a2. | the synthesis of a dithiolester analog of phosphatidylcholine, 1,2-bis(heptanoylthio)-1,2-dideoxy-sn-glycerol-3-phosphocholine (thio pc), is described. starting with 1-trityl-sn-glycerol (prepared from d-mannitol), tosylation followed by displacement with potassium methyl xanthate gave a trithiocarbonate. reductive cleavage of the latter gave a 1,2-dithiol which was then acylated, detritylated, and esterified with choline phosphate. hydrolysis of thio pc by phospholipase a2 (naja naja) indicated ... | 1983 | 6655369 |
| [specificity of the nuclease from the venom of the middle asia cobra (naja naja oxiana) to the macrostructure of polyribonucleotides]. | | 2017 | 6312288 |
| [study of long-chain neurotoxins from naja naja siamensis and naja naja oxiana venoms by circular dichroism and fluorescence]. | cd and fluorescence spectroscopy were used to study the conformational mobility of long-chain neurotoxins from the venom of cobra naja naja siamensis and naja naja oxiana (stx and nt-i, respectively). microenvironment of tryptophan residues in these neurotoxins and their lysine-modified derivatives was also analyzed. ionization of his22 (pk 5,4-5,6) in stx influences the invariant trp29 microenvironment. no conformational change was observed on titration of single his residue situated in the c-t ... | 1983 | 6679782 |
| the interaction of dialkyl ether lecithins with phospholipase a2 (naja naja naja). | dialkyl lecithins are nonhydrolyzable substrate analogues for phospholipase a2 (naja naja naja). short chain dialkyl lecithins (which form monomers and micelles), and long chain ether-linked lecithins (which form bilayers or can be solubilized in detergent micelles) have been used to study phospholipase a2/phospholipid interactions. the results of gel filtration, 1h and 31p nmr spectroscopy, kinetic assays and uv difference spectroscopy show that binding of the ether-linked lecithins is independ ... | 1983 | 6687887 |