Conserved motifs II to VI of DNA helicase II from Escherichia coli are all required for biological activity.

Published

Journal Article

There are seven conserved motifs (IA, IB, and II to VI) in DNA helicase II of Escherichia coli that have high homology among a large family of proteins involved in DNA metabolism. To address the functional importance of motifs II to VI, we employed site-directed mutagenesis to replace the charged amino acid residues in each motif with alanines. Cells carrying these mutant alleles exhibited higher UV and methyl methanesulfonate sensitivity, increased rates of spontaneous mutagenesis, and elevated levels of homologous recombination, indicating defects in both the excision repair and mismatch repair pathways. In addition, we also changed the highly conserved tyrosine(600) in motif VI to phenylalanine (uvrD309, Y600F). This mutant displayed a moderate increase in UV sensitivity but a decrease in spontaneous mutation rate, suggesting that DNA helicase II may have different functions in the two DNA repair pathways. Furthermore, a mutation in domain IV (uvrD307, R284A) significantly reduced the viability of some E. coli K-12 strains at 30 degrees C but not at 37 degrees C. The implications of these observations are discussed.

Full Text

Duke Authors

Cited Authors

  • Zhang, G; Deng, E; Baugh, LR; Hamilton, CM; Maples, VF; Kushner, SR

Published Date

  • December 1997

Published In

Volume / Issue

  • 179 / 23

Start / End Page

  • 7544 - 7550

PubMed ID

  • 9393722

Pubmed Central ID

  • 9393722

Electronic International Standard Serial Number (EISSN)

  • 1098-5530

International Standard Serial Number (ISSN)

  • 0021-9193

Digital Object Identifier (DOI)

  • 10.1128/jb.179.23.7544-7550.1997

Language

  • eng