BIOCHEMICAL-CHARACTERIZATION OF ESCHERICHIA-COLI DNA HELICASE-I

The gene product of F tral is a bifunctional protein which nicks and unwinds the F plasmid during conjugal DNA transfer. Further biochemical characterization of the Tral protein reveals that it has a second, much lower, K(m) for ATP hydrolysis, in addition to that previously identified. Measurement of the single-stranded DNA-stimulated ATPase rate indicates that there is co-operative interaction between the enzyme monomers for maximal activity. Furthermore, O-18-exchange exchange experiments indicate that Tral protein hydrolyses ATP with, at most, a low-level reversal of the hydrolytic step during each turnover.