Characterization of DNA polymerase I*, a form of DNA polymerase I found in Escherichia coli expressing SOS functions.

Abstract:

DNA polymerase I* is a form of the DNA polymerase I isolated from Escherichia coli which are expressing recA/lexA (SOS) functions. Induction of recA or polA1 cells by nalidixic acid does not result in the appearance of pol I*, but lexA or recA mutants that are constitutive for SOS functions constitutively express pol I* and mutants which lack functional recA protein produce pol I* when they carry a lexA mutation which renders the lexA repressor inoperative. Pol I* has been induced by nalidixic acid in dinA, dinD, dinF, and umuC mutants. Polymerase I* has a lower affinity for single-stranded DNA-agarose than polymerase I and it sediments through sucrose gradients in a dispersed manner between 6.6-10.5 S, whereas polymerase I sediments at 5 S. Whereas pol I* migrates significantly faster than pol I in nondenaturing polyacrylamide gels, the active polypeptide of both forms migrates at the same rate in denaturing polyacrylamide gels. Compared with polymerase I, polymerase I* has an enhanced capacity to incorporate the adenine analog, 2-amino-purine, into activated salmon sperm DNA and a relatively low fidelity in replicating synthetic polydeoxyribonucleotides. Both the 3'----5' (proofreading) and 5'----3' (nick-translational) exonuclease activities of pol I* and pol I are indistinguishable. Estimates of processivity give a value of approximately 6 for both forms of the enzyme.

Polymerases:

Topics:

Historical Protein Properties (MW, pI, ...), Nucleotide Incorporation, Exonuclease Activity, Source / Purification

Status:

new topics/pols set partial results complete validated

Results:

Polymerase Reference Property Result Context
Eco Pol I Lackey D1985 3-5' Exonuclease (proofreading) Yes
Eco Pol I Lackey D1985 Cloned or native Native organism
Eco Pol I Lackey D1985 5-3' Exonuclease Yes
Eco Pol I Lackey D1985 Full length or truncated Full length
Eco Pol I Lackey D1985 Processivity 6bp
Eco Pol I Lackey D1985 Specific Activity 25 units/mg
Eco Pol I* Lackey D1985 3-5' Exonuclease (proofreading) Yes
Eco Pol I* Lackey D1985 Cloned or native Native organism
Eco Pol I* Lackey D1985 5-3' Exonuclease Yes
Eco Pol I* Lackey D1985 Full length or truncated Full length
Eco Pol I* Lackey D1985 Processivity 6bp

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