Figure 1.

General scheme of a two-substrate experiment to measure rate enhancement of slow-turnover enzymes by proteins moving along DNA. (A) DNA glycosylase (OGG1 or NEIL1 in our experiments) is bound to the unlabeled primary substrate; in the absence of other enzymes it turns over slowly; (B) DNA polymerase (or other protein of interest) and the labeled secondary substrate is added; (C) DNA polymerase displaces the DNA glycosylase, which binds and cleaves the secondary substrate. Red asterisk denotes the radioactive label at the 5′-terminus.