A single-strand specific endonuclease activity copurifies with overexpressed T5 D15 exonuclease.
Nucleic Acids Res, 1991/8/11;19(15):4127-32.
Sayers JR[1], Eckstein F
Affiliations
PMID: 1651477
Impact factor: 19.16
Abstract
The T5 D15 exonuclease purified from an overproducing strain of E. coli was shown to possess a low level of endonucleolytic activity specific for single-stranded DNA when assayed with 1-10 mM Mg2+ as co-factor. Endonuclease activity on double-stranded circular DNA could not be detected under these conditions. Nicked circular DNA was first gapped by the enzyme's exonucleolytic activity, creating a single-stranded region. This gapped substrate was then endonucleolytically cleaved and rapidly degraded. We show that a gapped and not a nicked substrate is required for this activity as previously suggested (Moyer, R. W. and Roth, C. T. 1977, J. Virol. 24, 177-193). The single-strand endonuclease activity could be selectively suppressed by using low concentrations of Mg2+ as co-factor (less than 1 mM), thus allowing nicked double-stranded circular DNA to be gapped to a single-stranded circular species. We also report on sequence similarities between the T5 exonuclease and several prokaryotic DNA polymerases.
MeSH terms
Amino Acid Sequence; Base Sequence; DNA; DNA, Circular; DNA, Single-Stranded; DNA-Directed DNA Polymerase; Endonucleases; Escherichia coli; Exodeoxyribonucleases; Magnesium; Molecular Sequence Data; T-Phages; Transfection; Viral Plaque Assay
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