Irina Lehman

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DNA ligase of E. coli is a polypeptide of molecular weight 75,000. The comparable T4-induced enzyme is somewhat smaller (63,000 to 68,000). Both enzymes catalyze the synthesis of phosphodiester bonds between adjacent 5'-phosphoryl and 3'-hydroxyl groups in nicked duplex DNA, coupled to the cleavage of the pyrophosphate bond of DPN (E. coli) or ATP (T4).(More)
Both single- and double-stranded DNA stimulate the hydrolysis of ATP catalyzed by the recA protein of Escherichia coli. However, the reactions differ in their pH optima, response to recA protein concentration, salt sensitivity, and degree of inhibition by ADP, all of which reflect different requirements for the prehydrolytic binding of single- and(More)
The single-stranded DNA-binding protein of Escherichia coli significantly alters the strand assimilation reaction catalyzed by recA protein [McEntee, K., Weinstock, G. M. & Lehman, I. R. (1979) Proc. Natl. Acad. Sci. USA 76, 2615--2619]. The binding protein (i) increases the rate and extent of strand assimilation into homologous duplex DNA, (ii) enhances(More)
The recA protein of Escherichia coli promotes the complete exchange of strands between full-length linear duplex and single-stranded circular DNA molecules of bacteriophage phi X-174, converting more than 50% of the single-stranded DNA into heteroduplex replicative form II-like structures. Kinetically, the reaction can be divided into two phases, formation(More)
A 4-kilobase DNA fragment carried by a recombinant lambda gt11 bacteriophage appears to contain most of the coding information for the 145-kDa subunit of the Saccharomyces cerevisiae mitochondrial RNA polymerase. The RPO41 gene is located on chromosome VI, as determined by hybridization to electrophoretically separated yeast chromosomes. Hybridization and(More)
The Herpesviridae comprise a large class of animal viruses of considerable public health importance. Of the Herpesviridae, replication of herpes simplex virustype-1 (HSV-1) has been the most extensively studied. The linear 152-kbp HSV-1 genome contains three origins of DNA replication and approximately 75 open-reading frames. Of these frames, seven encode(More)
The herpes simplex virus type 1 (HSV-1) origin binding protein, the product of the UL9 gene, catalyzes the unwinding of DNA in the 3'-5' direction. Helicase activity is coupled to the hydrolysis of ATP or dATP and to a lesser extent to CTP, dCTP, or UTP. It requires a divalent cation (Mg2+ > Mn2+ > Ca2+) with an optimum at 2.5 mM MgCl2. Activity is optimal(More)
The deoxyribonuclease specified by the recB and recC genes of Escherichia coli (recBC DNase; exonuclease V) has been purified to near homogeneity by a new procedure. Although hydrolysis of even a single nucleotide from a duplex DNA molecule by the pure enzyme is absolutely dependent upon ATP, the extent of phosphodiester hydrolysis is strongly inhibited by(More)
Our earlier studies had suggested that endonuclease G (EndoG), a member of the evolutionarily conserved DNA/RNA nonspecific betabetaalpha-Me-finger nuclease family, functioned in the a sequence-mediated segment inversion observed during herpes simplex virus 1 replication. To test this hypothesis, we used RNA interference to reduce the level of EndoG in(More)