title: Cobalt: an effector of E. coli recA protein activity.
abstract: Studies of cation requirements in the recA-catalyzed proteolysis of lambda repressor and strand assimilation reactions have demonstrated that Co2+ significantly enhances both activities. In the presence of 4mM MgCl2, the optimal concentration of CoCl2 for proteolysis was 1mM. 2mM Co2+ increased the rate and extent of D-loop formation as measured by membrane filtration. Cobalt did not replace Mg2+ for the ssDNA-dependent ATPase activity of recA, and did not affect the rate of hydrolysis of ATP, measured over a wide range of DNA concentrations. Cobalt did prevent the Mg-dependent ssDNA renaturation catalyzed by recA protein. Membrane filter binding assays established that Co2+ increases the affinity of recA protein for ssDNA with ATP, dATP, or ATP gamma S as cofactors. The dissociation of recA protein from ssDNA-nucleoside triphosphate complex was much slower with CoCl2. This metal provides an excellent tool for dissecting the various activities inherent in recA protein.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002413:Cations, Divalent; D003035:Cobalt / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D011938:Rec A Recombinases
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; D003035:Cobalt; D011938:Rec A Recombinases; D000251:Adenosine Triphosphatases