Highly selective affinity labeling of the primer-binding site of E. coli DNA polymerase I.

Highly selective affinity labeling of the primer site of E. coli DNA polymerase I was performed with the 5'-reactive derivatives of oligothymidylate in the presence of poly(dA) template. Subtilysine cleavage proved that the site of affinity modification belonged to the 'Klenow' part of DNA polymerase I. If taken separately, Klenow fragment was not labeled by these oligonucleotide derivatives. The site of affinity labeling were tested in the structure of DNA polymerase I by hydroxylamine cleavage. At least two sites of labeling were revealed. The main one was localized between Gly-833 and His-928.