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cloning and expression of the gene for the vitamin b12 receptor protein in the outer membrane of escherichia coli.the transport of cyanocobalamin (vitamin b12) in cells of escherichia coli is dependent on a receptor protein (btub protein) located in the outer membrane. a 9.1-kilobase pair bamhi fragment carrying the btub gene was cloned from a specialized transducing phage into multicopy plasmids. insertions of transposon tn1000 which prevented production of the receptor localized btub to a 2-kilobase pair region. further subcloning allowed isolation of this region as a 2.3-kilobase pair sau3a fragment. the ...19852982793
the dna region of phage bf23 encoding receptor binding protein and receptor blocking lipoprotein lacks homology to the corresponding region of closely related phage t5.analysis of the dna region upstream of the bf23 hrs gene revealed a genetic organisation similar to that of closely related phage t5. a gene encoding a lipoprotein (llp(bf23)) is located directly upstream of the gene encoding the receptor binding protein (hrs) but is transcribed in opposite direction. the gene is followed by four open reading frames transcribed in the same direction. the llp (bf23) gene product does not show similarity to the corresponding t5 llp(t5) protein, however, like llp(t ...200616598825
deletions or duplications in the btub protein affect its level in the outer membrane of escherichia coli.the escherichia coli btub product is an outer membrane protein that mediates the tonb-coupled active transport of cobalamins and the uptake of the e colicins and bacteriophage bf23. the roles of various segments of the btub protein in its function or cellular localization were investigated by analysis of several genetic constructs. hybrid proteins in which various lengths from the amino terminus of btub were linked to alkaline phosphatase (btub::phoa genes) were all secreted across the cytoplasm ...19911885541
identity of genes a2 and a3 of bacteriophage bf23.the polypeptide coded by gene a3 of bacteriophage bf23 has been purified and its n-terminal amino acid sequence determined. this sequence is identical to the n-terminal sequence of the polypeptide coded by gene a2. the two gene products have identical molecular weight. we conclude that these two gene products are identical, and are coded by one and the same gene, namely gene a2-a3, which was previously thought to be two genes, a2 and a3.19902196744
cloning, sequencing, and expression of bacteriophage bf23 late genes 24 and 25 encoding tail proteins.two bacteriophage bf23 late genes, genes 24 and 25, were isolated on a 7.4-kb psti fragment from the phage dna, and their nucleotide sequences were determined. gene 24 encodes a minor tail protein with the expected m(r) of 34,309, and gene 25 located 4 bp upstream of gene 24 encodes a major tail protein with the expected m(r) of 50,329. when total cellular rna isolated from either phage-infected cells or cells bearing the cloned genes was analyzed by the primer extension method using the primers ...19947961500
growth of coliphage bf23 on rough strains of salmonella typhimurium: the bfe locus.coliphage bf23 develops in salmonella typhimurium rough strains. the phage is neither restricted nor modified by s. typhimurium. the growth patterns of the phage were slightly different in s. typhimurium than in escherichia coli, although phage propagated on s. typhimurium is identical to the phage propagated in e. coli by several criteria used. mutants of s. typhimurium resistant to bf23 were isolated and found to map (by p22- and pl-mediated transduction) in the same position as bfe mutants of ...1976787757
nucleotide sequence of a dna fragment that contains the abi gene of the colib plasmid.a 1989-bp psti dna fragment from the colib plasmid, which contains the abi gene that is necessary for the abortive response to infections by bacteriophage bf23 or t5, was sequenced. a candidate open reading frame for the abi gene has been suggested on the basis of a shine-dalgarno sequence appropriately placed ahead of its atg initiation codon, a promoter upstream from the shine-dalgarno sequence, and a location compatible with deletion mapping. the polypeptide that would be coded by this open r ...19883072577
physical and genetic analyses of the inc-i alpha plasmid r64.a 126-kilobase (kb) physical and genetic map of the inc-i alpha plasmid r64 was constructed by using the restriction enzymes, bamhi, sali, xhoi, hindiii, and ecori. the replication (rep) and incompatability (inc) functions of this plasmid were located in a 1.75-kb segment of an ecori fragment, e10 (3.3 kb). in addition, the genes determining growth inhibition of phage bf23 (ibf), suppression of dnag ( sog ), resistance to tetracycline (tetr), and resistance to streptomycin ( strr ) were located ...19846327656
conserved structural and regulatory regions in the salmonella typhimurium btub gene for the outer membrane vitamin b12 transport protein.the salmonella typhimurium btub gene encodes an outer membrane protein that is necessary for the transport of vitamin b12 and the uptake of the e colicins and bacteriophage bf23. the sequence of this gene showed 87% identity of the deduced polypeptide to its escherichia coli homolog, and its product was found to function in transport as effectively in cells of e. coli as did the native protein. the extensive sequence conservation within the first 300 transcribed nucleotides, which include the le ...19921448622
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