Campus Units

Zoology, Molecular, Cellular and Developmental Biology, Genetics

Document Type

Article

Publication Version

Published Version

Publication Date

1994

Journal or Book Title

Biochemistry

Volume

33

Issue

13

First Page

3841

Last Page

3847

DOI

10.1021/bi00179a007

Abstract

A novel DNA helicase isolated from Xenopus laevis ovaries [Poll, E. H. A., & Benbow, R. M. (1988) Biochemistry 27,8701—8706] was characterized biochemically. The directionality of DNA unwinding was determined to be 3' to 5'. A short 3' ssDNA tail adjacent to duplex DNA was required for DNA unwinding; the minimum length of this tail was between four and nine bases. Only short duplex DNA regions were unwound: duplex DNA of 16 base pairs was readily unwound, whereas a 26 base pair duplex was not. Longer duplex regions were unwound in the presence of Escherichia coli single-strand DNA binding protein if, in addition, the duplex region was flanked by an unpaired 3' or 5' tail and the substrate resembled a branched replicative intermediate. X. laevis DNA helicase I exhibited high affinity for ssDNA, moderate affinity for dsDNA, and no affinity for RNA. DNA unwinding activity was stimulated by monovalent cations, with an optimal concentration of 150 mM for NaCl or KC1 or 125 mM for Na*P04 or KxP04. The ATP analog ATP7S inhibited the DNA unwinding and copurifying DNA-dependent ATPase activity, whereas AMPPCP and AMPPNP moderately inhibited DNA unwinding activity and had little effect on the copurifying DNA-dependent ATPase activity. CTP was a relatively strong inhibitor of DNA unwinding activity, but GTP, UTP, dCTP, dGTP, or TTP showed moderate or no inhibition. The copurifying DNA-dependent ATPase activity was not inhibited by CTP, GTP, UTP, dCTP, dGTP, or TTP.

Comments

Reprinted (adapted) with permission from Xenopus laevis Ovarian DNA Helicase I: A 3' to 5' Helicase That Unwinds Short Duplexes. E. H. A. Poll, Jeff Harrison, Angela Umthun, Drena L. Dobbs, and Robert M. Benbow. Biochemistry 1994 33 (13), 3841-3847. DOI: 10.1021/bi00179a007. Copyright 1994 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Share

COinS