| recognition site of escherichia coli b restriction enzyme on phi xsb1 and simian virus 40 dnas: an interrupted sequence. | methyl groups placed on varphixsb1 replicative form dna by the escherichia coli b modification enzyme are located in the overlap between fragments mbo ii-3 and alu i-2, a 61-base-pair dna segment. mutations that led to loss of susceptibility to restriction by e. coli b occurred within this segment at three positions spanning 14 nucleotides. a sequence difference between varphixsb1 and varphixam3cs70, a varphix174 strain not restricted by e. coli b, occurs at one of these positions. the site on s ... | 1978 | 209460 |
| interaction of deoxycholate and of detergents with the coat protein of bacteriophage f1. | the major coat protein of bacteriophage f1, which is localized in the host membrane during phage maturation, has a hydrophobic binding site capable of binding deoxycholate and a variety of detergents to form a soluble particle, and in that respect, resembles many membrane proteins. the soluble particle has properties that suggest it is formed by simple insertion of protein into a deoxycholate or detergent micelle, but molecular weight measurements show that the protein is present as a dimer, eve ... | 1975 | 1092689 |
| membrane localization and topology of a viral assembly protein. | the gene i protein (pi) of the filamentous bacteriophage f1 is required for the assembly of this virus. antibodies specific to either the amino or carboxyl terminus of this protein were used to determine the location and topology of the gene i protein in f1-infected bacteria. pi is anchored in the inner membrane of escherichia coli cells via a 20-amino-acid hydrophobic stretch, with its carboxyl-terminal 75 residues located in the periplasm and its amino-terminal 253 amino acids residing in the ... | 1992 | 1556066 |
| pexpress: a family of expression vectors containing a single transcription unit active in prokaryotes, eukaryotes and in vitro. | we have constructed a family of expression vectors containing a single transcription unit that is active in escherichia coli, eukaryotic cells, and in coupled in vitro transcription-translation systems. these vectors use the rous sarcoma virus-long terminal repeat (rsv-ltr) as the promoter/enhancer for eukaryotic cells. in vitro transcription is made possible by inclusion of a bacteriophage t7 promoter. this same promoter is actively transcribed in e. coli that produce t7 rna polymerase. other f ... | 1991 | 1657716 |
| improved expression vectors for eukaryotic promoter/enhancer studies. | we describe two transfectable vectors designed to facilitate the functional analysis of eukaryotic promoter/enhancer sequences. the first, pjfcat1, is an improved chloramphenicol acetyltransferase (cat) reporter gene expression vector with two features that distinguish it from the majority of other cat vectors currently in use: 1) it carries a trimer cassette of the simian virus 40 major late polyadenylation site to block plasmid-initiated read-through expression of cat, and 2) it includes the p ... | 1991 | 1725108 |
| enhanced secretion from insect cells of a foreign protein fused to the honeybee melittin signal peptide. | the baculovirus/insect cell system has been remarkably successful in yielding high levels of synthesis of many proteins which have been difficult to synthesize in other host/vector systems. the system is also capable of secreting heterologous proteins, but with generally low efficiency. we have increased the efficiency of secretion of the system by using signal peptides of insect origin to direct the secretion of a foreign protein. the precursor of the plant cysteine protease papain (propapain) ... | 1991 | 2016060 |
| translation initiation potential of the 5' proximal augs of the polycistronic p/c mrna of sendai virus. a multipurpose vector for site-specific mutagenesis. | to determine the translation initiation potential of the 5' proximal four augs of the polycistronic p/c mrna of sendai virus, we have developed an efficient system for oligonucleotide-directed site-specific mutagenesis utilizing a plasmid vector which contains the replication origin of the single-stranded dna phage f1 and the phage sp6 promoter. utilizing uridine containing single-stranded dna templates of the plasmid vector carrying the p/c gene we introduced point mutations in all four of the ... | 1988 | 2832411 |
| expression vectors permitting cdna cloning and enrichment for specific sequences by hybridization/selection. | a set of vectors is described which allow the efficient cloning of full-length cdnas, using a modification of the method of okayama and berg [mol. cell biol. 2 (1982) 161-170], and enrichment of specific sequences directly from cdna libraries by hybridization/selection. the vectors pcdpolyb+ and pcdpolyb- are derived from an expression vector described previously [okayama and berg, mol. cell biol. 3 (1983) 280-289] and allow expression of cloned cdnas in eukaryotic cells from the simian virus 40 ... | 1988 | 2843427 |
| plasmid pfce4: a new system of escherichia coli expression-modification vectors. | two versatile expression-modification vectors were obtained by inserting the origin of replication (ori) of phage f1 into the expression vector pots. the resulting plasmids produce large amounts of coding or noncoding ssdna (depending on ori orientation in pfce4+ and pfce4-) and excrete it into the medium as virus-like particles following infection with phage f1. these features make them suitable for dideoxy chain termination sequencing, oligonucleotide directed mutagenesis and gene expression w ... | 1985 | 3908223 |
| targeted mutagenesis in vitro: lac repressor mutations generated using amv reverse transcriptase and dbrutp. | we have cloned the gene for the lac operon repressor (laci) of escherichia coli into the m13 related phage f1. mutagenesis of the laci gene was performed in vitro by filling dsdna molecules gapped over the laci gene with avian myeloblastosis virus (amv) reverse transcriptase. laci mutants are found at a frequency of 1 in 10(4) using a genetic screen in vivo. for two-thirds of the 60 mutants, lesions were identified within the first 400 bases of laci, by dideoxy sequencing. an unexpectedly wide r ... | 1984 | 6203097 |
| sites of predicted stress-induced dna duplex destabilization occur preferentially at regulatory loci. | this paper describes a computational method to predict the sites on a dna molecule where imposed superhelical stresses destabilize the duplex. several dna sequences are analyzed in this way, including the pbr322 and cole1 plasmids, bacteriophage f1, and the polyoma and bovine papilloma virus genomes. superhelical destabilization in these molecules is predicted to occur at small numbers of discrete sites, most of which are within regulatory regions. the most destabilized sites include the termina ... | 1993 | 8385354 |
| virulence evolution in a virus obeys a trade-off. | the evolution of virulence was studied in a virus subjected to alternating episodes of vertical and horizontal transmission. bacteriophage f1 was used as the parasite because it establishes a debilitating but non-fatal infection that can be transmitted vertically (from a host to its progeny) as well as horizontally (infection of new hosts). horizontal transmission was required of all phage at specific intervals, but was prevented otherwise. each episode of horizontal transmission was followed by ... | 1999 | 10097397 |
| distribution of fitness effects caused by single-nucleotide substitutions in bacteriophage f1. | empirical knowledge of the fitness effects of mutations is important for understanding many evolutionary processes, yet this knowledge is often hampered by several sources of measurement error and bias. most of these problems can be solved using site-directed mutagenesis to engineer single mutations, an approach particularly suited for viruses due to their small genomes. here, we used this technique to measure the fitness effect of 100 single-nucleotide substitutions in the bacteriophage f1, a f ... | 2010 | 20382832 |
| interchangeability of related proteins and autonomy of function. the morphogenetic proteins of filamentous phage f1 and ike cannot replace one another. | the filamentous phage f1 and ike infect a common host, are structurally highly similar and exhibit 55% identity at the dna sequence level. based on the idea that proteins that function autonomously will be more tolerant of multiple amino acid differences than proteins that must interact with other proteins to function, the ability of four individual proteins from f1 to substitute for their ike equivalents to promote virus assembly in vivo has been examined. the reciprocal replacements were also ... | 1992 | 1404363 |
| a genetic selection for temperature-sensitive variants of the gene v protein of bacteriophage f1. | complementary negative and positive genetic selections based on the activity of a plasmid-encoded bacteriophage f1 gene v are developed. the negative selection is based on an activity of the gene v protein in e. coli cells which markedly reduces the infection of those cells by f1-related viruses. in order to select against cells expressing active gene v protein, the cells are infected with the p'age r386, a derivative of f1 which confers resistance to chloramphenicol, and are plated in the prese ... | 1988 | 3262864 |