Cloning and DNA sequence of plasmid determinant iss, coding for increased serum survival and surface exclusion, which has homology with lambda DNA

Summary Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters.     

Microbial transformation of rifamycin B: A new extracellular oxidase fromCurvularia lunata

Summary A highly active extracellular rifamycin oxidase was isolated fromCurvularia lunata var.aeri. The enzyme has a pH optimum of 6.5 and temperature optimum of 50°C.     

A physical and genetic map of the IncFI plasmid ColV2-K94

A restriction enzyme map of the IncFI plasmid ColV2-K94 was generated using EcoRI, BamHI, HindIII, and XhoI; the genetic features of this element were then mapped from previous heteroduplex studies.     

Isolation of monoclonal antibodies specific for human c-myc proto-oncogene product.

Six monoclonal antibodies have been isolated from mice immunized with synthetic peptide immunogens whose sequences are derived from that of the human c-myc gene product. Five of these antibodies precipitate p62c-myc from human cells, and three of these five also recognize the mouse c-myc gene product. None of the antibodies sees the chicken p110gag-myc protein. All six antibodies recognize immunoblotted p62c-myc. These reagents also provide the basis for an immunoblotting assay by which to quantitate p62c-myc in cells.     

Molecular epidemiology of plasmid patterns in Shigella dysenteriae type I obtained from an outbreak in West Bengal (India)

Abstract Multiple antibiotic-resistant Shigella dysenteriae type 1 isolates from a recent epidemic in West Bengal (India) showed identical plasmid patterns. All isolates were resistant to ampicillin (Am), chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm) and trimethoprim (Tp) and contained 6 plasmids, ranging from 2.5–120 kb. The Am resistance determinant was located on the 120 kb plasmid. This plasmid was unstable when the S. dysenteriae strains were grown above 37°C. The Bangladesh strains of S. dysenteriae type 1 showed identical plasmid patterns, except that many isolates were Am-sensitive and lacked the 120 kb plasmid. In strains from both Bangladesh and West Bengal, predominantly group-B plasmids conferred resistance to Cm and Tc. Comparisons of Eco R1 fragments generated from the total plasmid DNA content of each strain support the view that the plasmids present in the S. dysenteriae type 1 strains isolated from all recent epidemics in India and Bangladesh were identical.     

Contributions of traT and iss genes to the serum resistance phenotype of plasmid ColV2-K94

Abstract A genetic determinant for serum resistance, designated iss , has been found previously on the colicinogenic plasmid ColV2-K94. In this work we have identified a second serum resistance gene, traT , on ColV2-K94. The serum resistance mediated by derivatives of ColV2-K94 was due to presence of one or both of the iss and traT genes. Plasmid pWS12 (TraT⁺ Iss⁺) contained the kanamycin (Km) resistance transposon Tn 903 inserted near the origin of replication of ColV2-K94, and plasmids pWS15 (TraT⁺), pWS16 (TraT⁺) and pWS18 (TraT⁺ Iss⁺) were deletion derivatives of pWS12 constructed in vitro and in vivo. pWS12 and pWS18 conferred a 20-fold increase in relative resistance to 20% guinea pig serum when introduced into the serum-susceptible, genetically defined recA strain of Escherichia coli K-12, AB2463. Plasmids pWS15 and pWS16, from which iss had been deleted, still conferred 5-fold increases in relative resistance on AB2463. The level of resistance conferred on this strain by the antibiotic resistance plasmid R100–1 (which expresses the traT serum resistance gene) was comparable to that of plasmids pWS15 and pWS16. The 25-kDa traT gene product was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the outer membrane proteins of strain AB2463 carrying ColV2-K94. This protein cross-reacted immunologically with the traT protein expressed by F or R100–1. Our results indicated that both traT and iss are capable of mediating serum resistance in ColV2-K94.     

Bifunctionality and pseudoisozymes of pyruvate kinase from codfish muscle

Pyruvate kinase has been purified from codfish muscle. The ratio of phosphotransferase and oxalacetate decarboxylase activities remains relatively constant throughout purification steps. These two activities are dependent as well as sensitive to sulfhydryl reagents. In the presence of dithioerythritol, only one molecular form of pyruvate kinase is detected. However, the enzyme exists as four pseudoisozymes in the presence of 2-mercaptoethanol. The pseudoisozymes of codfish pyruvate kinase are interconvertible under the influence of sulfhydryl reagents.