Publications

escherichia coli dna polymerase iv mutator activity: genetic requirements and mutational specificity.	the dinb gene of escherichia coli is known to be involved in the untargeted mutagenesis of lambda phage. recently, we have demonstrated that this damage-inducible and sos-controlled gene encodes a novel dna polymerase, dna pol iv, which is able to dramatically increase the untargeted mutagenesis of f' plasmid. at the amino acid level, dna pol iv shares sequence homologies with e. coli umuc (dna pol v), rev1p, and rad30p (dna polymerase eta) of saccharomyces cerevisiae and human rad30a (xpv) prot ...	2000	10913093
the crystal structure of nusb from mycobacterium tuberculosis.	both prokaryotes and eukaryotes regulate transcription through mechanisms that suppress termination signals. an antitermination mechanism was first characterized in bacteriophage lambda. bacteria have analogous machinery that regulates ribosomal rna transcription and employs host factors, called the n-utilizing (where n stands for the phage lambda n protein) substances (nus), nusa, nusb, nuse and nusg. here we report the crystal structure of nusb from mycobacterium tuberculosis, the bacterium th ...	2000	10881194
proteolysis of bacteriophage lambda cii by escherichia coli ftsh (hflb).	ftsh (hflb) is a conserved, highly specific, atp-dependent protease for which a number of substrates are known. the enzyme participates in the phage lambda lysis-lysogeny decision by degrading the lambda cii transcriptional activator and by its response to inhibition by the lambda ciii gene product. in order to gain further insight into the mechanism of the enzymatic activity of ftsh (hflb), we identified the peptides generated following proteolysis of the phage lambda cii protein. it was found ...	2000	10809689
genetic system for reversible integration of dna constructs and lacz gene fusions into the escherichia coli chromosome.	a plasmid system for site-specific integration into and excision and recovery of gene constructs and lacz gene fusions from the escherichia coli chromosome was developed. plasmid suicide vectors utilizing the origin of replication of r6k plasmids and containing the attp sequence of bacteriophage lambda, multiple cloning site, and antibiotic resistance markers facilitate reversible integration into the e. coli chromosome by site-specific recombination. additional vectors permit construction of la ...	2000	10610816
a mutation correcting the dna interaction defects of a mutant phage lambda terminase, gpnu1 k35a terminase.	terminase, the dna packaging enzyme of bacteriophage lambda, is a heteromultimer composed of gpnu1 (181 aa) and gpa (641 aa) subunits, encoded by the lambda nu1 and a genes, respectively. similarity between the deduced amino acid sequences of gpnu1 and gpa and the nucleotide binding site consensus sequence suggests that each terminase subunit has an atp reactive center. terminase has been shown to have two distinct atpase activities. the gpnu1 subunit has a low-affinity atpase stimulated by nons ...	1999	10600592
a genetic screen to identify sequences that mediate protein oligomerization in escherichia coli.	many proteins assemble as oligomeric complexes and in several cases a distinct domain mediates the interaction between the subunits. the identification of new oligomerization modules is relevant to comprehend both the architecture and the evolution of protein sequences and also for protein engineering applications. using the bacteriophage lambda repressor dimerization assay, we searched escherichia coli genomic libraries for sequences able to mediate protein oligomerization in vivo. we identifie ...	1999	10581196
functional importance of regions in escherichia coli elongation factor nusa that interact with rna polymerase, the bacteriophage lambda n protein and rna.	the association of the essential escherichia coli protein nusa with rna polymerase increases pausing and the efficiency of termination at intrinsic terminators. nusa is also part of the phage lambda n protein-modified antitermination complex that functions to prevent transcriptional termination. we have investigated the structure of nusa using various deletion fragments of nusa in a variety of in vitro assays. sequence and structural alignments have suggested that nusa has both s1 and kh homolog ...	1999	10564494
addiction modules and programmed cell death and antideath in bacterial cultures.	in bacteria, programmed cell death is mediated through "addiction modules" consisting of two genes. the product of the second gene is a stable toxin, whereas the product of the first is a labile antitoxin. here we extensively review what is known about those modules that are borne by one of a number of escherichia coli extrachromosomal elements and are responsible for the postsegregational killing effect. we focus on a recently discovered chromosomally borne regulatable addiction module in e. co ...	1999	10547685
background mutations and polymorphisms in lacz-plasmid transgenic mice.	transgenic animal models harboring chromosomally integrated shuttle vectors with bacterial reporter genes are now widely used to measure in vivo mutant frequencies. the lacz-plasmid transgenic mouse model has a unique sensitivity to large rearrangements compared to systems using bacteriophage lambda vectors, which mainly detect point mutations and small deletions or insertions. in this study, the background mutant frequencies and spectra in the lacz-plasmid transgenic mouse model were investigat ...	1999	10529734
minicircle: an improved dna molecule for in vitro and in vivo gene transfer.	minicircles are a new form of supercoiled dna molecule for nonviral gene transfer which have neither bacterial origin of replication nor antibiotic resistance marker. they are thus smaller and potentially safer than the standard plasmids currently used in gene therapy. they were obtained in e. coli by att site-specific recombination mediated by the phage lambda integrase, which was used to excise the expression cassette from the unwanted plasmid sequences. we produced two minicircles containing ...	1999	10435105
regulation of copy number and stability of phage lambda derived ptc lambda 1 plasmid in the light of the dimer/multimer catastrophe hypothesis.	the dimer catastrophe hypothesis has been proposed previously to explain instability of multicopy plasmids whose partitioning is random, contrary to low copy number plasmids which are stably maintained and actively partitioned. until now, this hypothesis has been investigated using multicopy cole1 plasmids. however, for more detailed testing of the dimer/multimer catastrophe hypothesis, one should use a plasmid which can be maintained at either low or high copy number and still possesses the sam ...	1999	10427732
evidence for a holin-like protein gene fully embedded out of frame in the endolysin gene of staphylococcus aureus bacteriophage 187.	we have cloned, sequenced, and characterized the genes encoding the lytic system of the unique staphylococcus aureus phage 187. the endolysin gene ply187 encodes a large cell wall-lytic enzyme (71.6 kda). the catalytic site, responsible for the hydrolysis of staphylococcal peptidoglycan, was mapped to the n-terminal domain of the protein by the expression of defined ply187 domains. this enzymatically active n terminus showed convincing amino acid sequence homology to an n-acetylmuramoyl-l-alanin ...	1999	10419939
replication of bacteriophage lambda in the escherichia coli dnaa deltarac hosts.		1999	10328680
cloning of mycoplasma synoviae genes encoding specific antigens and their use as species-specific dna probes.	a genomic library of mycoplasma synoviae (ms) was generated by using bacteriophage lambda gt11 as a cloning and expression vector. identification of recombinant clones highly specific to ms was achieved by screening the library for expression of ms proteins with polyclonal antiserum that had been preadsorbed with 6 heterologous avian mycoplasma species antigens. expression of the recombinant clones in escherichia coli followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the t ...	1999	10098689
crystallographic analysis of the dsdna bacteriophage hk97 mature empty capsid.	hk97 is a member of the siphovirus family of dsdna bacteriophages. it is similar in architecture to bacteriophage lambda, the type member of this family, with an icosahedral capsid of triangulation number t = 7. no high-resolution structural information is available for the dsdna phages, and hk97 is the only dsdna bacteriophage capsid to produce crystals which diffract x-rays. at 650 a in diameter, the large size of the particle and resultant large unit cell create crystallographic challenges. t ...	1999	10089306
ftsh--a single-chain charonin?	the ftsh gene encodes an atp- and zn(2+)-dependent metalloprotease with a molecular mass of about 70 kda. it was first identified in escherichia coli where it is also designated hflb, tolz or mrsc, and seems to be present in most if not all bacteria. the ftsh protein is anchored to the cytoplasmic membrane via two transmembrane regions in such a way that the very short amino- and the long carboxy-termini are exposed into the cytoplasm. ftsh is member of the aaa family (atpases associated with a ...	1999	10077851
characterization of the recd gene of neisseria gonorrhoeae ms11 and the effect of recd inactivation on pilin variation and dna transformation.	pilin antigenic variation in neisseria gonorrhoeae may result following intrachromosomal recombination between homologous pil genes. despite extensive study, reca is the only previously characterized gene known to be involved in this process. in this study, the gonococcal recd gene, encoding one subunit of the putative recbcd holoenzyme, was characterized and its role in pilin variation assessed. the complete recd gene of n. gonorrhoeae ms11 was cloned and its nucleotide sequence determined. the ...	1999	10075421
cloning and expression in escherichia coli of an azoreductase gene from clostridium perfringens and comparison with azoreductase genes from other bacteria.	a genomic library of clostridium perfringens atcc 3626 was constructed in phage lambda gt11 and screened with an antibody against the c. perfringens azoreductase, which catalyzes the reduction of azo dyes to aromatic amines. a positive recombinant phage, containing a 3.8 kb dna fragment insert was selected and purified. lytic and lysogenic escherichia coli cultures infected with the recombinant phage had higher azoreductase activity than cultures infected only with the vector lambda gt11. the 3. ...	1999	10071864
malk forms a dimer independent of its assembly into the malfgk2 atp-binding cassette transporter of escherichia coli.	the maltose transport complex (mtc) is a member of the atp-binding cassette superfamily of membrane transport proteins and is a model for understanding the folding and assembly of hetero-oligomeric membrane protein complexes. the mtc is made up of two integral membrane proteins, malf and malg, and a peripheral membrane protein, malk. these proteins associate with a stoichiometry of 1:1:2 to form the complex malfgk2. in our studies of the oligomerization of this complex, we have shown that the at ...	1999	10037713
the geometry of a synaptic intermediate in a pathway of bacteriophage lambda site-specific recombination.	bacteriophage lambda uses site-specific recombination to move its dna into and out of the escherichia coli genome. the recombination event is mediated by the phage-encoded integrase (int) at short dna sequences known as attachment ( att ) sites. int catalyzes recombination via at least four distinct pathways, distinguishable by their requirements for accessory proteins and by the sequence of their substrates. the simplest recombination reaction catalyzed by int does not require any accessory pro ...	1999	9927749
formation of the preprimosome protects lambda o from rna transcription-dependent proteolysis by clpp/clpx.	using the bacteriophage lambda dna replication system, composed entirely of purified proteins, we have tested the accessibility of the short-lived lambda o protein to the clpp/clpx protease during the various stages of lambda dna replication. we find that binding of lambda o protein to its orilambda dna sequence, leading to the so-called "o-some" formation, largely inhibits its degradation. on the contrary, under conditions permissive for transcription, the lambda o protein bound to the orilambd ...	1998	9860956
identification and characterization of the fis operon in enteric bacteria.	the small dna binding protein fis is involved in several different biological processes in escherichia coli. it has been shown to stimulate dna inversion reactions mediated by the hin family of recombinases, stimulate integration and excision of phage lambda genome, regulate the transcription of several different genes including those of stable rna operons, and regulate the initiation of dna replication at oric. fis has also been isolated from salmonella typhimurium, and the genomic sequence of ...	1998	9811652
escherichia coli dnaa gene function and bacteriophage lambda replication.	allele specificity of the escherichia coli dnaa gene function in the replication of plasmids derived from bacteriophage lambda has been demonstrated previously. here, using a series of dnaa temperature-sensitive mutants, we investigated dnaa allele specificity of the replication of phages lambda p+ and lambda pts 1 pi a66. we found that phage lambda p+ produces its progeny efficiently at 43 degrees c irrespective of the dnaa allele, whereas lambda pts 1 pi a66, which is unable to develop lytical ...	1998	9785448
cloning and characterization of the dnak heat shock operon of the marine bacterium vibrio harveyi.	we cloned the dna region of the vibrio harveyi chromosome containing the heat shock genes dnak and dnaj and sequenced them. these genes are arranged in the chromosome in the order dnak-dnaj, as in other proteobacteria of the alpha and gamma subdivisions. the dnak gene is 1923 nucleotides in length and codes for a protein of 640 amino acid residues, with a predicted molecular mass of 69,076 da and 81.2% similarity to the dnak protein of escherichia coli. the v. harveyi dnaj gene has a coding sequ ...	1998	9747709
the ihf mrna levels decline as neisseria gonorrhoeae enters the stationary growth phase.	integration host factor (ihf) is a small heterodimeric dna binding protein found in all gram-negative bacteria and is implicated as a transcription cofactor of pile in neisseria gonorrhoeae (hill, s.a., samuels, d.s., carlson, j.h., wilson, j., hogan, d., lubke, l., belland, r.j., 1997. integration host factor is a transcriptional cofactor of pile in neisseria gonorrhoeae. mol. microbiol. 23, 649-656). the ihf genes (ihfa and ihfb) were cloned from n. gonorrhoeae through functional complementati ...	1998	9714829
rapid degradation of polyadenylated oop rna.	the oop rna is a short (77 nucleotides (nt)) transcript encoded by bacteriophage lambda which acts as an antisense rna for lambda cii gene expression. recently we demonstrated that oop rna is specifically polyadenylated at its 3' end by poly(a) polymerase i (pap i), the pcnb gene product. here we demonstrate that the half life of oop rna is 3 times longer in the pcnb mutant relative to the pcnb+ host, indicating that polyadenylation of this transcript causes its accelerated degradation. although ...	1998	9710253
the escherichia coli rna polymerase alpha subunit and transcriptional activation by bacteriophage lambda cii protein.	bacteriophage lambda is not able to lysogenise the escherichia coli rpoa341 mutant. this mutation causes a single amino acid substitution lys271glu in the c-terminal domain of the rna polymerase alpha subunit (alphactd). our previous studies indicated that the impaired lysogenisation of the rpoa341 host is due to a defect in transcriptional activation by the phage cii protein and suggested a role for alphactd in this process. here we used a series of truncation and point mutants in the rpoa gene ...	1998	9701520
biochemical and genetic analysis of lambdaw, the newly isolated lambdoid phage.	otherwise isogenic escherichia coli cp78 (rela+) and cp79 (rela-) strains are commonly used in studies on the stringent control, the bacterial response to amino acid starvation. we found that these strains are lysogenic for a phage which is spontaneously induced with a low frequency, producing virions able to infect other e. coli strains. genetic studies, restriction analysis of the phage dna genome, and electron microscopy revealed that this phage is very similar to, but not identical with, bac ...	1998	9701518
oligohistidine tag mutagenesis of the lambda holin gene.	holins are a diverse group of small integral membrane proteins elaborated by bacteriophages to lyse bacterial hosts and effect release of progeny phages in a precisely timed manner. recently, the holin s gene of phage lambda was overexpressed and the holin protein was purified to homogeneity by means of an oligohistidine tag procedure and immobilized metal affinity chromatography (d. l. smith, d. k. struck, j. m. scholtz, and r. young, j. bacteriol. 180:2531-2540, 1998). numerous locations withi ...	1998	9696770
inactivation of bacteriophage lambda, escherichia coli, and candida albicans by ozone.	the effects of ozone (o3) on three types of microbes were studied. test suspensions were exposed to 600 ppm o3 at room temperature. control experiments were performed under identical conditions using oxygen gas. bacteriophage lambda was completely inactivated at 10 min while escherichia coli and candida albicans were only inactivated by factors of 10(5) and 10(4) respectively at 40 min. exposure of a mixed microbial suspension to o3 for 5 min resulted in 100% killing of bacteriophages while the ...	1998	9684309
mutations affecting cooperative dna binding of phage hk022 ci repressor.	cooperative protein-dna interactions play critical roles in gene regulation in all organisms. among the best-studied cooperative interactions is that of phage lambda repressor, which binds cooperatively to two adjacent operators. similar cooperative interactions are also shown by several other lambdoid phage repressors, including hk022 ci repressor, which we study here. this protein has a much higher degree of cooperativity than seen with lambda repressor, and previous evidence has suggested tha ...	1998	9636698
the helicobacter felis ftsh gene encoding an atp-dependent metalloprotease can replace the escherichia coli homologue for growth and phage lambda lysogenization.	cloning and sequencing of an approximately 6.0-kb chromosomal dna fragment from helicobacter felis revealed five complete open reading frames. the deduced amino acid sequence of one orf exhibited sequence similarity to the ftsh protein, an atp-dependent metalloprotease, from various bacterial species. the encoded protein consists of 638 amino acid residues with a molecular mass of 70.2 kda. the hydropathy profile of the ftsh protein predicted two n-terminal transmembrane regions that were confir ...	1998	9560419
specific binding of escherichia coli ribosomal protein s1 to boxa transcriptional antiterminator rna.	we show that ribosomal protein s1 specifically binds the boxa transcriptional antiterminator rnas of bacteriophage lambda and the escherichia coli ribosomal rna operons. although s1 competes with the nusb-s10 antitermination complex for binding to boxa, it does not affect antitermination by the lambda n protein in vitro, and its role, if any, in rrna synthesis is still unknown.	1998	9555913
dnaa-stimulated transcriptional activation of orilambda: escherichia coli rna polymerase beta subunit as a transcriptional activator contact site.	we present evidence that escherichia coli rna polymerase beta subunit may be a transcriptional activator contact site. stimulation of the activity of the pr promoter by dnaa protein is necessary for replication of plasmids derived from bacteriophage lambda. we found that dnaa activates the pr promoter in vitro. particular mutations in the rpob gene were able to suppress negative effects that certain dnaa mutations had on the replication of lambda plasmids; this suppression was allele-specific. w ...	1998	9539721
guanosine tetraphosphate (ppgpp)-mediated inhibition of the activity of the bacteriophage lambda pr promoter in escherichia coli.	it was previously demonstrated that the activity of bacteriophage lambda promoter pr is decreased in wild-type escherichia coli cells starved for amino acids (during the stringent response). since pr activity is necessary for the transcriptional activation of ori lambda, this leads to inhibition of the replication of plasmids derived from phage lambda. these results led to the proposal that the pr promoter susceptible to control by the stringent response. however, subsequent studies demonstrated ...	1998	9529531
crystallization and preliminary x-ray analysis of the dsdna bacteriophage hk97 mature empty capsid.	hk97 is a temperate dsdna bacteriophage of escherichia coli that is structurally similar to phage lambda, with an icosahedral head of triangulation (7) number 7. although the capsids of several large dsdna phages have been studied extensively using a variety of biophysical approaches, no high-resolution structure is available. we have grown crystals of mature but empty bacteriophage hk97 capsids that diffract to at least 3.5 a using synchrotron radiation. the hk97 head ii crystals are the first ...	1998	9527920
design and implementation of a qualitative simulation model of lambda phage infection.	motivation: molecular biology databases hold a large number of empirical facts about many different aspects of biological entities. that data is static in the sense that one cannot ask a database 'what effect has protein a on gene b?' or 'do gene a and gene b interact, and if so, how?'. those questions require an explicit model of the target organism. traditionally, biochemical systems are modelled using kinetics and differential equations in a quantitative simulator. for many biological process ...	1998	9520505
changes in the periplasmic linker and in the expression level affect the activity of toxr and lambda-toxr fusion proteins in escherichia coli.	in order to assess the potentiality of vibrio cholerae toxr protein and of bacteriophage lambda repressor as indicators of the dimerization of periplasmic proteins in escherichia coli, we have constructed a series of plasmids encoding transmembrane fusion proteins. the amino-terminal part, containing the dna binding domain of either toxr or lambda repressor, is located in the cytoplasm and acts as reporter for dimerization. as models of periplasmic proteins we have used alkaline phosphatase (a d ...	1998	9515742
escherichia coli nusa is required for efficient rna binding by phage hk022 nun protein.	the nun protein of phage hk022 is an rna binding protein of the arginine-rich motif family. nun binds the phage lambda boxb rna sequence (boxb) on nascent lambda transcripts and arrests transcription elongation. binding to boxb is inhibited by zn2+ and stimulated by the escherichia coli nusa protein. deletion of the nun c-terminal region enhances boxb binding and makes it independent of zn2+ and nusa. the c terminus of nun thus appears to interfere with the n-terminal rna binding motif. nusa rel ...	1998	9465052
involvement of boxa nucleotides in the formation of a stable ribonucleoprotein complex containing the bacteriophage lambda n protein.	the association of the transcriptional antitermination protein n of bacteriophage lambda with escherichia coli rna polymerase depends on nut site rna (boxa + boxb) in the nascent transcript and the host protein, nusa. this ribonucleoprotein complex can transcribe through rho-dependent and intrinsic termination sites located up to several hundred base pairs downstream of nut. for antitermination to occur farther downstream, this core antitermination complex must be stabilized by the host proteins ...	1998	9461609
mutation of d. radiodurans in a gene homologous to ruvb of e. coli.	following the digestion of chromosomal dna of deinococcus radiodurans with a restriction enzyme a partial genomic library was constructed using lambda phage as a vector. a phage clone whose dna can complement the deficiency in a radiation-sensitive mutant of d. radiodurans was isolated. following the subcloning using phasmid vector, a hybrid plasmid containing 1.2 kb inserted dna was obtained. after the determination of nucleotide sequence, the deduced amino acid sequence showed close homology t ...	1997	9447236
the xcpr protein of pseudomonas aeruginosa dimerizes via its n-terminus.	extracellular protein secretion by the main terminal branch of the general secretory pathway in pseudomonas aeruginosa requires a secretion machinery comprising the products of at least 12 genes. one of the components of this machinery, the xcpr protein, belongs to a large family of related proteins distinguished by the presence of a highly conserved nucleotide binding domain (walker box a). the xcpr protein is essential for the process of extracellular secretion and amino acid substitutions wit ...	1997	9426126
regulation of the elongation-termination decision at intrinsic terminators by antitermination protein n of phage lambda.	the mechanisms that control n-protein-dependent antitermination in the phage lambda life cycle have counterparts in the regulatory systems of other organisms. here we examine n-dependent antitermination at the intrinsic tr' terminator of lambda to elucidate the regulatory principles involved. the tr' terminator consists of a sequence of six base-pairs along the template at which the transcription complex is sufficiently destabilized to make rna release possible. within this "zone of opportunity" ...	1997	9367773
chi-star, a chi-related 11-mer sequence partially active in an e. coli recc1004 strain.	chi sequence (5'gctggtgg) of escherichia coli was first identified as a site that increased the plaque size of bacteriophage lambda. subsequent studies showed that this site is responsible for both the attenuation ofrecbcd exonuclease activity and the promotion of reca, recbcd-mediated recombination. it is known that bacteriophage lambda containing the chi site makes very small plaques on a recc* (recc1004) mutant because chi is not recognized by the recbc*d mutant enzyme.	1997	9348042
roles for lambda orf and escherichia coli reco, recr and recf in lambda recombination.	bacteriophage lambda lacking its red recombination functions requires either its own gene product, orf, or the product of escherichia coli's reco, recr and recf genes (recorf) for efficient recombination in recbc sbcb sbcc mutant cells (the recf pathway). phage crosses under conditions of a partial block to dna replication have revealed the following: (1) in the presence of orf, recf pathway recombination is similar to lambda red recombination; (2) orf is necessary for focusing recombination tow ...	1997	9335578
oriented dna binding by one-armed lambda repressor heterodimers and contacts between repressor and rna polymerase at p(rm).	bacteriophage lambda repressor activates transcription from p(rm) by contacting the sigma subunit of e. coli rna polymerase. although mutations in repressors that are defective in activation affect exposed residues in the repressor-operator co-crystal, the subunit in repressor dimers that is responsible for activation has not been determined experimentally. here, we describe an oriented heterodimer approach using one-armed repressor-leucine zipper fusion proteins to resolve this question. protec ...	1997	9282743
long-range effects in a supercoiled dna domain generated by transcription in vitro.	the translocation of a transcription complex can transiently introduce positive and negative superhelical windings into the template dna. to gain further insight into this dynamic dna supercoiling mechanism and its possible involvement in biological processes, we employed an in vitro system in which site-specific recombination by gammadelta resolvase is topologically coupled to transcription-induced negative supercoiling. our kinetic experiments suggest that recombination is closely linked to th ...	1997	9281422
cloning, expression, and mutagenesis of trypsin inhibitor etib from erythrina variegata seeds.	erythrina variegata trypsin inhibitors designated etia and etib belong to the kunitz family trypsin inhibitor, but etia is unique in its ability to inhibit tissue-type plasminogen activator, while etib is not. the cdna clone encoding etib was isolated from the seed cdna library constructed in the lambda phage lambda gt11. the etib cdna insert consists of 765 bp, including an open reading frame of 606 pb from atg to tga codons. the deduced amino acid sequence consists of 202 amino acids, having t ...	1997	9214769
genetic and transcriptional analysis of flgb flagellar operon constituents in the oral spirochete treponema denticola and their heterologous expression in enteric bacteria.	oral spirochetes possess many potential virulence factors, including the capacity for tissue invasion and persistence despite a vigorous host immune response. in an attempt to identify treponemal immunoreactive components, sera derived from individuals with advanced periodontal disease were used as a reagent to isolate recombinant bacteriophage lambda clones expressing antigens of the oral spirochete treponema denticola atcc 35405. nucleotide sequence analysis of a clone expressing three immunor ...	1997	9169730
protein interaction cloning by far-western screening of lambda-phage cdna expression libraries.		1997	9116852
immunological screening of lambda-phage cdna expression libraries.		1997	9116850
gene replacement with linear dna fragments in wild-type escherichia coli: enhancement by chi sites.	during conjugation and transduction of escherichia coli even numbers of recombinational exchanges are required for replacement of a gene on the circular chromosome. we studied gene replacement using a related method of gene transfer (transformation with 6.5-kb linear dna fragments) as an experimental model for conjugation and transduction. two properly situated chi sites, 5' gctggtgg 3', stimulated gene replacement approximately 50-fold, more than the sum of the stimulation by the individual chi ...	1997	9093843
cloning and characterization of bacteriophage-like dna from haemophilus somnus homologous to phages p2 and hp1.	in an attempt to identify and characterize components of a heme uptake system of haemophilus somnus, an escherichia coli cosmid library of h. somnus genomic dna was screened for the ability to bind hemin (hmb+). the hmb+ phenotype was associated with a 7,814-bp hindiii fragment of h. somnus dna that was subcloned and sequenced. thirteen open reading frames (orfs) were identified, all transcribed in one direction, and transposon mutagenesis identified orf7 as the gene associated with the hmb+ phe ...	1997	9068631
a novel bacterial vector system for monitoring protein-protein interactions in the camp-dependent protein kinase complex.	a bacterial expression vector is described for investigation of protein-protein interactions. important features of the vector include partition of the ci repressor of bacteriophage lambda into two functional domains separated by a multicloning site, and low level auto-regulated expression of human genes as c-terminal fusions to the dna-binding domain of ci. two different reporter systems have been employed; expression of either a suppressor trna or the alkaline phosphatase gene is dependent in ...	1997	9034306
[lux-regulon from vibrio fisheri reduces type 1 restriction in escherichia coli k12 cells].	the ecok restriction of nonmodified phage lambda.0 controlled by escherichia coli k12 lon- cells is alleviated 10-20-fold in the presence of a hybrid plasmid containing the entire lux regulon of vibrio fischeri. the la protease participates in degradation of the regulatory luxr-luxi proteins; therefore, transcription of the right lux operon begins significantly earlier than in the lon+ bacteria and is characterized by high content of the n-(3-oxohexanoyl) homoserine lactone autoinducer in medium ...	1996	8964486
identification and characterization of the escherichia coli rbn gene encoding the trna processing enzyme rnase bn.	the gene encoding rnase bn was localized to 88 min on the escherichia coli chromosome by a novel suppressor assay and conjugational and transductional analysis. assay of subclones derived from lambda phage 543 of the kohara library, which encompasses this region of the chromosome, for elevated rnase bn activity identified o290, a previously reported open reading frame, as the gene encoding rnase bn. interruption of this gene with a kan(r) cassette and introduction into the chromosome eliminated ...	1996	8955422
modulation of lambda integrase synthesis by rare arginine trna.	lambda's int gene contains an anomalously high frequency of the rare arginine codons aga and agg when compared to genes of escherichia coli or to the rest of phage lambda. these are the least frequent codons in genes of e. coli and are recognized by the rarest trnas. the presence of these codons reduces the translation rate and, depending on the context, this can strongly modulate translational efficiency by a variety of mechanisms. in this study, we show that expression of the natural int gene ...	1996	8843435
conjugative transposon tn916: evidence for excision with formation of 5'-protruding termini.	conjugative transposons are genetic elements able to promote their own intracellular transposition and intercellular conjugal transfer. they move by an excision-integration system related to that of lambdoid phages, in which the first step is the excision of the transposon from the donor replicon to form a covalently closed circular intermediate which contains a heteroduplex joint. in this work, sequencing both strands of the circular intermediate heteroduplex joint, it was found that, as during ...	1996	8824634
device for the simultaneous screening of bacteriophage lambda clones.		1996	8770396
[organization of the gene for the beta-subunit of human photoreceptor cyclic gmp phosphodiesterase].	two recombinant bacteriophage lambda clones encoding a 27.8-kb fragment of the human phosphodiesterase beta-subunit gene were isolated from a human genomic library. the nucleotide sequences of 19 exons (from the 4th to 22nd), 18 introns, and the 3'-flanking region were determined. the analysis of the nucleotide sequence of the phosphodiesterase beta-subunit gene revealed four alu repeats and four minisatellite regions.	1996	8768262
function of e. coli rna polymerase sigma factor sigma 70 in promoter-proximal pausing.	the sigma factor sigma 70 of e. coli rna polymerase acts not only in initiation, but also at an early stage of elongation to induce a transcription pause, and simultaneously to allow the phage lambda gene q transcription antiterminator to act. we identify the signal in dna that induces early pausing to be a version of the sigma 70 -10 promoter consensus, and we show that sigma 70 is both necessary for pausing and present in the paused transcription complex. regions 2 and 3 of sigma 70 suffice to ...	1996	8756730
transcription antitermination: the lambda paradigm updated.	coliphage lambda employs systems of transcription termination and antitermination to regulate gene expression. early gene expression is regulated by the phage-encoded n protein working with a series of escherichia coli proteins, nus, at rna sites, nut, to modify rna polymerase to a termination-resistant form. expression of lambda late genes is regulated by the phage-encoded q antitermination protein. q, which appears to use only one host factor, acts at a dna site, qut, to modify rna polymerase ...	1995	8709839
rho-dependent termination of transcription is governed primarily by the upstream rho utilization (rut) sequences of a terminator.	a rho-dependent transcription terminator in escherichia coli dna consists of an upstream part for rho utilization (rut) and the transcription stop point (tsp) region. to test the role of the tsp region variants of the coliphage lambda cro gene terminator, tr1, containing inserts of non-terminator sequences between its rut and tsp regions were tested for termination function. the results showed that termination occurred with high efficiency at multiple sites in each of the new sequences with the ...	1996	8702947
the rna chain elongation rate of the lambda late mrna is unaffected by high levels of ppgpp in the absence of amino acid starvation.	in this study, the effects of high levels of guanosine tetraphosphate (ppgpp) on the decay and rna chain elongation kinetics of the bacteriophage lambda late transcript in escherichia coli were examined in the absence of amino acid starvation. the accumulation, mrna decay kinetics, and rna chain elongation rate of the lambda late mrna were determined after heat induction of lambdaci857 lysogens in the presence of high levels of ppgpp induced from a relaalpha fragment-overproducing plasmid. the a ...	1996	8663373
identification of functional regions of the nun transcription termination protein of phage hk022 and the n antitermination protein of phage lambda using hybrid nun-n genes.	phages lambda and hk022 express proteins n and nun, respectively, each of which acts with a number of escherichia coli host nus factors at lambda nut rna sites, to influence transcription elongation. the lambda nut sites, nearly identical sequences located downstream of the early promoters, pl and pr, were first identified as cis-acting signals required for the action of n in forming termination-resistant transcription complexes. surprisingly, the nun protein, resembling n and expressed by anoth ...	1996	8632463
escherichia coli thymidylate kinase: molecular cloning, nucleotide sequence, and genetic organization of the corresponding tmk locus.	thymidylate kinase (dtmp kinase; ec 2.7.4.9) catalyzes the phosphorylation of dtmp to form dtdp in both de novo and salvage pathways of dttp synthesis. the nucleotide sequence of the tmk gene encoding this essential escherichia coli enzyme is the last one among all the e. coli nucleoside and nucleotide kinase genes which has not yet been reported. by subcloning the 24.0-min region where the tmk gene has been previously mapped from the lambda phage 236 (e9g1) of the kohara e. coli genomic library ...	1996	8631667
long-circulating bacteriophage as antibacterial agents.	the increased prevalence of multidrug-resistant bacterial pathogens motivated us to attempt to enhance the therapeutic efficacy of bacteriophages. the therapeutic application of phages as antibacterial agents was impeded by several factors: (i) the failure to recognize the relatively narrow host range of phages; (ii) the presence of toxins in crude phage lysates; and (iii) a lack of appreciation for the capacity of mammalian host defense systems, particularly the organs of the reticuloendothelia ...	1996	8622911
role of escherichia coli rna polymerase alpha subunit in modulation of pausing, termination and anti-termination by the transcription elongation factor nusa.	the alpha subunit (alpha) of rna polymerase (rnap) is critical for assembly of polymerase and positive control of transcription initiation in escherichia coli. here, we report that alpha also plays a role in transcription elongation, and this involves a direct interaction between alpha and nusa factor. during in vitro transcription without nusa, alpha interacts with the nascent rna, as revealed by photocrosslinking. when nusa is present, rna crosslinks to nusa rather than to alpha. we show that ...	1996	8598198
transformation of naturally competent streptococcus mutans with replicative and non-replicative tn916-containing plasmids: implications for a mechanism of transposition.	based on the observations reported here and what is known concerning transformation of naturally competent strains of s. mutans and other streptococcal species such as s. gordonii, we propose the model shown in figure 2. the tn916-intermediate transforms s. mutans as originally proposed for b. subtilis by scott and coworkers [8]. it is not clear in either system (b. subtilis or s. mutans) whether the tn916 intermediate enters the cell as ds-dna or ss-dna. because it is likely that transformation ...	1995	8586174
functional analysis of isolated cpn10 domains and conserved amino acid residues in spinach chloroplast co-chaperonin by site-directed mutagenesis.	the possibilities of independent function of the two chaperonin 10 (cpn10) domains of the cpn10 homologue from spinach chloroplasts and the role of five conserved amino acid residues in the n-terminal cpn10 unit were investigated. recombinant single domain proteins and complete chloroplast cpn10 proteins carrying amino acid exchanges of conserved residues in their n-terminal cpn10 domain were expressed in escherichia coli and partially purified. the function of the recombinant proteins was teste ...	1995	8555447
biosynthetic incorporation of 7-azatryptophan into the phage lambda lysozyme: estimation of tryptophan accessibility, effect on enzymatic activity and protein stability.	the phage lambda lysozyme (lambda l) contains four tryptophans. these have been efficiently replaced by 7-azatryptophan (7aw) through biosynthetic incorporation into the overexpressed protein. comparative analysis of the effect of temperature or ph on the fluorescence of the wild-type lambda l and 7aws-containing protein (a lambda l) shows that the stability of the protein is only mildly reduced by 7aw incorporation above ph 5 but that it is strongly decreased below ph 4 on protonation of inacce ...	1995	8532666
expression of the escherichia coli ftsz gene: trials and tribulations of gene fusion studies.	the ftsz gene of escherichia coli, which codes for an essential cell division protein, is subjected to multiple regulation, as shown in part with studies using an ftsz::lacz operon fusion located on phage lambda jfl100. using this same fusion, we sought to isolate regulatory mutants overexpressing ftsz by selecting mutants able to grow on lactose. one lac+ mutant was obtained which overexpressed the ftsz::lacz fusion 70-fold. the mutation responsible for the overexpression lies in a new gene, co ...	1993	8468005
identification of algf in the alginate biosynthetic gene cluster of pseudomonas aeruginosa which is required for alginate acetylation.	mucoid strains of pseudomonas aeruginosa produce a high-molecular-weight exopolysaccharide called alginate that is modified by the addition of o-acetyl groups. to better understand the acetylation process, a gene involved in alginate acetylation called algf was identified in this study. we hypothesized that a gene involved in alginate acetylation would be located within the alginate biosynthetic gene cluster at 34 min on the p. aeruginosa chromosome. to isolate algf mutants, a procedure for loca ...	1993	8394313
localization and nucleotide sequences of genes mediating site-specific recombination of the slp1 element in streptomyces lividans.	slp1 is a 17.2-kbp genetic element indigenous to the streptomyces coelicolor chromosome. during conjugation, slp1 can undergo excision and subsequent site-specific integration into the chromosomes of recipient cells. we report here the localization, nucleotide sequences, and initial characterization of the genes mediating these recombination events. a region of slp1 adjacent to the previously identified site of integration, attp, was found to be sufficient to promote site-specific integration of ...	1993	8387993
targeted mutagenesis of dna using triple helix-forming oligonucleotides linked to psoralen.	oligonucleotides can bind as third strands of dna in a sequence-specific manner in the major groove in homopurine/homopyrimidine stretches in duplex dna. here we use a 10-base triplex-forming oligonucleotide linked to a psoralen derivative at its 5' end to achieve site-specific, targeted mutagenesis in an intact, double-stranded lambda phage genome. site-specific triplex formation delivers the psoralen to the targeted site in the lambda dna, and photoactivation of the psoralen produces adducts a ...	1993	8356097
an analogue of the dnaj molecular chaperone in escherichia coli.	escherichia coli dnaj functions as a typical molecular chaperone in coordination with other heat shock proteins such as dnak and grpe in a variety of cellular processes. in this study, it was found that e. coli possesses an analogue of dnaj, as judged from not only its primary structure but also its possible function. this protein, named cbpa (for curved dna-binding protein), was first identified as a dna-binding protein that preferentially recognizes a curved dna sequence. cloning and nucleotid ...	1994	8302830
from the double-helix to novel approaches to the sequencing of large genomes.	elucidation of the structure of dna by watson and crick [nature 171 (1953) 737-738] has led to many crucial molecular experiments, including studies on dna replication, transcription, physical mapping, and most recently to serious attempts directed toward the sequencing of large genomes [watson, science 248 (1990) 44-49]. i am totally convinced of the great importance of the human genome project, and toward achieving this goal i strongly favor 'top-down' approaches consisting of the physical map ...	1993	8276270
expression and biochemical properties of a protein serine/threonine phosphatase encoded by bacteriophage lambda.	the predicted amino acid sequence encoded by the open reading frame 221 (orf221) of bacteriophage lambda exhibited a high degree of similarity to the catalytic subunits of a variety of protein serine/threonine phosphatases belonging to pp1, pp2a, and pp2b groups. cloning and expression of the orf221 gene in escherichia coli provided direct evidence that the gene codes for a protein serine/threonine phosphatase. the single-subunit recombinant enzyme was purified in soluble form and shown to posse ...	1993	8248155
bacterially expressed fabs of monoclonal antibodies neutralizing tumour necrosis factor alpha in vitro retain full binding and biological activity.	antibody fragments specific for the human tumour necrosis factor alpha (tnf alpha) have been cloned from lambda combinatorial expression libraries using total rna obtained from three different hybridoma cell lines of therapeutic interest. the previously described bacteriophage lambda vectors, lambda hc2 and lambda lc1, were modified to create unique antibody cloning sites in the combinatorial construct and a novel tag peptide was inserted at the c-terminal end of the expressed fd chain. sequence ...	1993	8232337
generating bacteriophage lambda sublibraries enriched for rare clones.		1994	8185914
generation of bacteriophage lambda lysogens by electroporation.		1994	8179876
synthesis and assembly of the f0 proton channel from f0 genes cloned into bacteriophage lambda and integrated into the escherichia coli chromosome.	the promoter region and the first four genes of the escherichia coli proton-translocating atpase (unc) operon, uncibef, were cloned into bacteriophage lambda, enabling this region to be recombined into an unc-deleted e. coli chromosome at the lambda att site. the resultant e. coli strain, carrying single-copy f0 genes, was tested for synthesis and assembly of functional f0 proton channels. membranes isolated from this strain contained all three f0 subunits and were capable of binding purified f1 ...	1994	8125942
[bacteriophage lambda:lux: design and expression of bioluminescence in e. coli cells].	the bacteriophages lambda:lux and lambda:luxab have been constructed by ligation of phage arms generated by bamhi or salgi restriction endonucleases digestion of embl4 to bamhi digested plasmid pf1 lux+ or to salgi digested plasmid pf2 lambda:luxa+b+. cells of escherichia coli prototrophic strain cs were infected with lambda:lux or lambda:luxab and intensity of bioluminiscence of the samples registered at different time intervals determined. the signal of bioluminiscence was first detected 15 mi ...	1994	8065385
functions involved in bacteriophage p2-induced host cell lysis and identification of a new tail gene.	successful completion of the bacteriophage p2 lytic cycle requires phage-induced lysis of its escherichia coli host, a process that is poorly understood. genetic analysis of lysis-deficient mutants defined a single locus, gene k, which lies within the largest late transcription unit of p2 and maps between head gene l and tail gene r. we determined and analyzed the dna sequence of a ca. 2.1-kb ecorv fragment that spans the entire region from l to r, thus completing the sequence of this operon. th ...	1994	8051010
inactivation and repair of bacteriophage lambda by furfural.	furfural is a dietary mutagen and is present in various frequently consumed food products. in earlier work we have shown that it induces single strand breaks in duplex dna which occur preferentially in at base pairs. experiments on the conservation of ecori cleavage site in mutant plasmids further established that repair of furfural damaged plasmid dna occurs on propagation in the host cells. in this paper it is shown that the strand scissions induced by furfural in dna account for its biologica ...	1994	8019442
the vibrio cholerae toxin-coregulated-pilus gene tcpi encodes a homolog of methyl-accepting chemotaxis proteins.	virulence gene activation in vibrio cholerae is under the control of the toxr-toxt regulatory cascade. the toxr regulon consists of genes required for toxin-coregulated-pilus (tcp) biogenesis, accessory colonization factor genes, cholera toxin genes, and toxr-activated genes (tag) of unknown function. the tagb gene was isolated by using a tagb::tnphoa fusion junction to probe a v. cholerae )395 bacteriophage lambda library. nucleotide sequence analysis revealed that tagb is identical to tcpi, a ...	1994	8005659
high-level expression of staphylococcal nuclease a in escherichia coli.	the staphylococcal nuclease a gene has been successfully cloned and overexpressed in e. coli under the transcriptional control of the bacteriophage lambda prpl promoters regulated by the temperature sensitive repressors. the sds-page analysis demonstrates that the nuclease a is produced to the extent of as much as 60% of the total cellular protein. the n-terminal analysis of the nuclease a shows that the amino terminal formyl methionine residue of the enzyme is precisely processed. the recombina ...	1994	7993969
topology of the product binding site in rna polymerase revealed by transcript slippage at the phage lambda pl promoter.	in the presence of transcription substrates atp, ctp, and utp, a stable ternary complex containing tetranucleotide auca is formed on the phage lambda pl promoter (starting sequence c-3a-2c-1a+1u+2c+3a+4g+5). we show that in the absence of gtp or at undersaturating gtp concentrations the auca transcript synthesized at the +1 to +4 segment slips back by 3 nucleotides and is stabilized in the ternary complex in such a way that only its 2 3'-proximal bases remain paired to the -1/+1 positions of the ...	1994	7989343
cloning and expression of the gene for group b streptococcal hyaluronate lyase.	group b streptococci (gbs) are a major cause of serious human perinatal infections. most clinical isolates of gbs secrete hyaluronate lyase, and production of high levels of the enzyme has been associated with strain virulence. degenerate oligonucleotide primers, designed on the basis of the amino acid sequences of tryptic peptides prepared from the purified enzyme, permitted the polymerase chain reaction amplification from gbs chromosomal dna of a 363-base pair internal dna fragment of the gbs ...	1994	7982914
a novel escherichia coli expression-export vector containing alkaline phosphatase as an insertional inactivation screening system.	an escherichia coli expression-export vector was constructed (pcgv1, 6.3 kb) containing the alkaline phosphatase structural gene (phoa) located downstream from the phage lambda pr and pl promoters positioned in tandem and the cits857 gene encoding lambda thermosensitive repressor. the phoa gene is fused to dna encoding a hybrid signal sequence that contains the n-terminal portion of the beta-lactamase (bla) signal sequence and the c-terminal region of the phoa signal sequence. within the dna enc ...	1994	7926833
the gene fimu affects expression of salmonella typhimurium type 1 fimbriae and is related to the escherichia coli trna gene argu.	the gene fimu, located on a recombinant plasmid carrying the salmonella typhimurium type 1 fimbrial gene cluster is closely related to the escherichia coli trna gene argu. the fimu gene complements an e. coli argu mutant that is a p2 lysogen, thereby allowing the phage p4 to grow in this strain but preventing the growth of phage lambda. in addition, fimu was shown to be involved in fimbrial expression since transformants of the e. coli argu mutant could produce fimbriae only in the presence of f ...	1994	7914347
repair of phage lambda dna damaged by near ultraviolet light plus 8-methoxypsoralen.	treatment of phage lambda with 8-methoxypsoralen plus near ultraviolet light (puva) and its subsequent infection and growth on various mutant and non-mutant hosts were investigated. a number of escherichia coli dna repair-deficient mutants, particularly those deficient in genes producing proteins known to participate in interstrand crosslink repair, were used as hosts to assess the roles of these gene products in the activation of phage affected by puva. results show that puva, uvra, uvrd, reca, ...	1995	7897361
very short patch repair of t:g mismatches in vivo: importance of context and accessory proteins.	in escherichia coli, t:g mismatches in specific contexts are corrected by a very short patch (vsp) repair system. previous studies have shown that the product of gene vsr mediates correction of t:g to c:g in the 5'ctagg/3'ggtcc context and in some related contexts. amber mutations that arose in cag sequences in gene ci of bacteriophage lambda were used to determine the effect of flanking bases on the repair of t:g mispairs arising during phage recombination. the experimental findings were combin ...	1995	7836300
cloning of the na(+)-translocating nadh-quinone reductase gene from the marine bacterium vibrio alginolyticus and the expression of the beta-subunit in escherichia coli.	the na(+)-translocating nadh-quinone reductase purified from the marine bacterium vibrio alginolyticus is composed of three subunits, alpha, beta and gamma. from the n-terminal amino acid sequences of each subunit and its polypeptide fragment obtained by partial digestion with v8 protease, oligonucleotides corresponding to forward and reverse primers for each gene (nqr a, b and c) encoding the alpha, beta and gamma subunit, respectively, were synthesized. using these primers, a part of each gene ...	1994	7805866
phage t4 dna [n6-adenine]methyltransferase. overexpression, purification, and characterization.	the bacteriophage t4 dam gene, encoding the dam dna [n6-adenine]methyltransferase (mtase), has been subcloned into the plasmid expression vector, pjw2. in this construct, designated pint4dam, transcription is from the regulatable phage lambda pr and pl promoters, arranged in tandem. a two-step purification scheme using deae-cellulose and phosphocellulose columns in series, followed by hydroxyapatite chromatography, was developed to purify the enzyme to near homogeneity. the yield of purified pro ...	1995	7782299
characterization of gene expression in recombinant escherichia coli cells infected with phage lambda.	phage lambda infection was investigated for possible production of toxic foreign proteins in escherichia coli. the target gene transcription was regulated by a t7 promoter, which was initiated under the action of t7 rna polymerase delivered by infecting phage. two types of phage infection were investigated. in both cases, deletion of the int gene prevents lysogenic integration. one phage, lambda ce6, contains the sam7 lysis mutation, so that infectious phage particles remain intracellular. the o ...	1993	7763591
production of a biologically active recombinant teleostean growth hormone in e. coli cells.	we have isolated and characterized several recombinant lambda phage clones carrying growth hormone (gh) cdna of striped bass (morone saxatilis). nucleotide sequence and the predicted amino acid sequence of sbgh was determined from a recombinant clone carrying the longest cdna insert. the sbgh cdna encodes a pre-hormone of 204 amino acid residues. comparison of the predicted amino acid sequence of sbgh with those of other vertebrates revealed different degrees of sequence identity: approximately ...	1995	7758842
cloning and expression of cdna encoding a protein that binds a palindromic promoter element essential for induction of fungal cutinase by plant cutin.	previous studies showed that a palindromic sequence located at -159 base pairs is essential for induction of cutinase gene in fusarium solani f. sp. pisi (nectria haematococca mating type vi) by the hydroxy fatty acids from plant cutin and that a 50-kda nuclear protein binds to a promoter that contains this element. screening of a phage lambda gt11 expression library with the concatenated palindromic sequence as the probe identified a cdna encoding a palindrome-binding protein (pbp). nucleotide ...	1995	7744822
the requirement for molecular chaperones in lambda dna replication is reduced by the mutation pi in lambda p gene, which weakens the interaction between lambda p protein and dnab helicase.	during the initiation of lambda dna replication, the host dnab helicase is complexed with phage lambda p protein in order to be properly positioned near the ori lambda-lambda o initiation complex. however, the lambda p-dnab interaction inhibits the activities of dnab. thus, the concerted action of bacterial heat shock proteins, dnak, dnaj, and grpe, is required to activate the helicase. wild-type phage lambda cannot grow on the e. coli dnab, dnak, dnaj, and grpe mutants. however, lambda phage wi ...	1995	7730358
the rhizobium meliloti groelc locus is required for regulation of early nod genes by the transcription activator nodd.	the molecular chaperones related to groel (hsp60, cpn60) interact with partially folded proteins and appear to assist them to attain active and correctly folded conformation. they are required for cell viability but are probably more important for some processes than for others. through a random genetic search to find loci that are required for expression of the rhizobium meliloti nod (nodulation) genes, we isolated a mutant (b4) defective in luteolin-dependent activation of nod gene expression, ...	1995	7729688