title: A single hydrophobic cleft in the Escherichia coli processivity clamp is sufficient to support cell viability and DNA damage-induced mutagenesis in vivo.
abstract: BACKGROUND
  The ubiquitous family of DnaN sliding processivity clamp proteins plays essential roles in DNA replication, DNA repair, and cell cycle progression, in part by managing the actions of the different proteins involved in these processes. Interactions of the homodimeric Escherichia coli β clamp with its known partners involves multiple surfaces, including a hydrophobic cleft located near the C-terminus of each clamp protomer.
  
  
  RESULTS
  A mutant E. coli β clamp protein lacking a functional hydrophobic cleft (βC) complemented the temperature sensitive growth phenotype of a strain bearing the dnaN159 allele, which encodes a thermolabile mutant clamp protein (β159). Complementation was conferred by a βC/β159 heterodimer, and was observed only in the absence of the dinB gene, which encodes DNA polymerase IV (Pol IV). Furthermore, the complemented strain was proficient for umuDC (Pol V)--dependent ultraviolet light (UV)--induced mutagenesis.
  
  
  CONCLUSIONS
  Our results suggest that a single cleft in the homodimeric E. coli β sliding clamp protein is sufficient to support both cell viability, as well as Pol III, Pol IV, and Pol V function in vivo. These findings provide further support for a model in which different Pols switch places with each other on DNA using a single cleft in the clamp.
authors.affiliation: Department of Biochemistry, and Witebsky Center for Microbial Pathogenesis and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, 3435 Main Street, 140 Farber Hall, Buffalo, NY 14214, USA. mdsutton@buffalo.edu
authors.forename: Mark D
authors.initials: MD
authors.lastname: Sutton
authors.forename: Jill M
authors.initials: JM
authors.lastname: Duzen
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Scouten Ponticelli
mesh_terms: D000483:Alleles; D004249:DNA Damage; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D050296:Microbial Viability; D016296:Mutagenesis; D010641:Phenotype; D014466:Ultraviolet Rays
chemical_list: C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; C101139:beta subunit, DNA polymerase III; D004258:DNA Polymerase III; D019951:DNA Polymerase beta; C120926:DNA polymerase V, E coli; D004259:DNA-Directed DNA Polymerase