3nct

Publication Abstract from PubMed

During bacterial conjugation, genetic material from one cell is transferred to another as single-stranded DNA. The introduction of single-stranded DNA into the recipent cell would ordinarily trigger a potentially deleterious transcriptional response called SOS, which is initiated by RecA protein filaments formed on the DNA. During F plasmid conjugation, however, the SOS response is suppressed by PsiB, an F-plasmid-encoded protein that binds and sequesters free RecA to prevent filament formation. Among the many characterized RecA modulator proteins, PsiB is unique in using sequestration as an inhibitory mechanism. We describe the crystal structure of PsiB from the Escherichia coli F plasmid. The stucture of PsiB is surprisingly similar to CapZ, a eukaryotic actin filament capping protein. Structure-directed neutralization of electronegative surfaces on PsiB abrogates RecA inhibition whereas neutralization of an electropositive surface element enhances PsiB inhibition of RecA. Together, these studies provide a first molecular view of PsiB and highlight its use as a reagent in studies of RecA activity.

X-ray crystal structure of the bacterial conjugation factor PsiB, a negative regulator of RecA.,Petrova V, Satyshur KA, George NP, McCaslin D, Cox MM, Keck JL J Biol Chem. 2010 Jul 21. PMID:20659894^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.