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Biomedical subjects

M L Gefter

Publications and source records attributed to M L Gefter.

At least 109 records · Page 6Linked to original sources
PubMed1973

A DNA-binding protein induced by bacteriophage T7.

A DNA-binding protein has been purified from Escherichia coli infected with bacteriophage T7 by DNA-cellulose chromatography. The protein is absent in uninfected cells. The purified protein has a molecular weight of 31,000 and binds strongly and preferentially to single-stranded DNA. In vitro studies show that this protein can stimulate the rate of polymerization catalyzed by the T7-induced DNA polymerase 10-15 times under conditions where the polymerase is unable to effectively use a single-stranded template. The degree of stimulation is dependent upon the ratio of binding protein to DNA template and is independent of polymerase concentration. The observed stimulation is specific for the T7 DNA polymerase in that addition of the protein to reactions catalyzed by E. coli DNA polymerases I, II, or III or T4 DNA polymerase is without effect.

Chromatography, Affinity↗
PubMed1972

A DNA-unwinding protein isolated from Escherichia coli: its interaction with DNA and with DNA polymerases.

A DNA-unwinding protein has been purified to homogeneity from E. coli. This protein has a molecular weight of about 22,000, as judged by its electrophoretic mobility on polyacrylamide gels containing sodium dodecylsulfate, and it appears to be present in about 800 copies per log-phase cell. It binds tightly and cooperatively to single-stranded DNA, and much less tightly, if at all, to RNA or double-stranded DNA. Like the T4 gene-32 protein characterized previously, the E. coli DNA-unwinding protein depresses the melting temperature of double-stranded DNAs, with regions rich in A-T base-pairs being preferentially melted. The E. coli protein strongly stimulates in vitro DNA synthesis by E. coli DNA polymerase II on appropriate templates; however, no stimulation is found with purified polymerases I or III of E. coli, or with T4 DNA polymerase. In contrast, gene-32 protein stimulates only the T4 DNA polymerase in a parallel assay.

Adenosine Triphosphate↗
PubMed1971

Analysis of DNA polymerases II and 3 in mutants of Escherichia coli thermosensitive for DNA synthesis.

A series of double mutants carrying one of the thermosensitive mutations for DNA synthesis (dnaA, B, C, D, E, F, and G) and the polA1 mutation of DeLucia and Cairns, were constructed. Enzyme activities of DNA Polymerases II and III were measured in each mutant. DNA Polymerase II activity was normal in all strains tested. DNA Polymerase III activity is thermosensitive specifically in those strains having thermoscnsitive mutations at the dnaE locus. From these results we conclude that DNA Polymerases II and III are independent enzymes and that DNA Polymerase III is an enzyme required for DNA replication in Escherichia coli.

Chromatography↗
PubMed1971

Purification and DNA synthesis in cell-free extracts: properties of DNA polymerase II.

The major DNA-synthesizing enzyme present in Pol A(1) (-)Escherichia coli (DNA polymerase II) has been purified to homogeneity as judged by polyacrylamide gel electrophoresis. The enzyme requires all four deoxynucleoside triphosphates, Mg(++), NH(4) (+), and native DNA for maximal activity. The enzyme activity is sensitive to sulfhydryl reagents and is insensitive to anti-DNA polymerase I antiserum. A second DNA-synthesizing enzyme, present in low amounts, has been identified in Pol A(1) (-) extracts. The relationship of this enzyme to DNA polymerases I and II is discussed.

Cell-Free System↗
PubMedDate not supplied

Analysis of the anti-azobenzenearsonate response at the molecular level.

We have analysed, at the molecular level, the antibodies associated with the anti-azobenzenearsonate response of A/J and BALB/c mice as well as the genes that encode them. All antibodies expressing the predominant idiotype are derived by somatic mutation from a single VH gene. Antibody molecules express the idiotype regardless of their light chains or the JH segments which encode them. The D segment, however, does seem to be important for idiotype expression. The anti-azobenzenearsonate antibodies possessing the minor idiotype (36-60) are encoded by single, highly homologous VH genes in A/J and BALB/c mice. The nucleotide sequences of the VH genes from these two strains show only two nucleotide disparities. However, as opposed to A/J mice, the 36-60 idiotype in BALB/c appears to be the dominant idiotype among anti-azobenzenearsonate antibodies.

Animals↗