Nucleic Acids Research, 1980, Vol. 8, No. 3 657-671
© 1980
Articles |
Mechanism of 3'
5' exonuclease associated with phage T5-induced DNA polymerase: processiveness and templete specificity
University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences, and Biology Division, Oak Ridge National Laboratory Oak Ridge, TN 37830, USA
Received August 27, 1979.
T5-induced DNA polymerase has an associated 3'
5' exonuclease activity. Both single-stranded and duplex DNA are hydrolyzed by this enzyme in a quasi-processive manner. This is indicated by the results of polymer-challenge experiments utilizing product analysis techniques. Due to the quasi-processive mode of hydrolysis, the kinetics of label release from the 3'-terminally labeled oligonucleotide substrates, annealed to complementary homopolymers, show an initial high rate of hydrolysis. In the case of both single-stranded and duplex DNA substrates, hydrolysis scene to continue, at best, up to the point where the enzyme is five or six nucleotides away from the 5'-end.
The enzyme carries out mismatch repair, as evidenced by experiments with primer molecules containing improper base residues at the 3'-OH terminus. Control experiments with complementary base residues at the 3'-end indicate that extensive removal of terminal residues takes place in the presence of dNTP's only when such residues are "improper" in the Watson-Crick sense.