New roles of DNA and SopB in polymerization of SopA of Escherichia coli F plasmid

This study followed kinetics of polymerization and de-polymerization of SopA by turbidity measurement and found new effects by DNA and SopB. Plasmid DNA, at low concentrations, shortened the lag (nucleation) phase of SopA polymerization and also caused an initial ‘burst’ of turbidity. Results with two non-specific 20-bp DNAs indicated sequence/length dependence of these effects. sopAB operator DNA only showed inhibition of SopA polymerization. Results of turbidity decrease of pre-formed SopA polymer in the presence of ethylenediaminetetraacetic acid showed that SopB also accelerates disassembly of the SopA polymer. The steady-state level of turbidity in the presence of SopB and plasmid DNA indicated synergy between SopB and DNA in the disassembly. SopB protein showed no effect on SopA polymerization, when SopB was specifically bound to DNA. This result and others with truncation mutants of SopB suggested that a proper configuration of the domains of SopB is important for SopA-SopB interactions.
Source: Journal of Biochemistry - Category: Biochemistry Authors: Tags: Regular Papers Source Type: research