Protease La from Escherichia coli hydrolyzes ATP and proteins in a linked fashion.

Abstract

The energy requirement for protein breakdown in E. coli results from an ATP requirement for the function of protease La, the product of the lon gene. This novel serine protease contains an ATPase activity that is essential for proteolysis. ATP and protein hydrolysis show the same Km for ATP (30-40 .mu.M) and are affected similarly by various inhibitors, activators and ATP analogs. Vanadate inhibited ATP cleavage and caused a proportionate reduction in casein hydrolysis, and inhibitors of serine proteases reduced ATP cleavage. Thus, ATP and protein hydrolysis appear to be linked stoichiometrically. ATP hydrolysis is stimulated 2- to 3-fold by polypeptides that are substrates for the protease (casein, glucagon) but not by nonhydrolyzed polypeptides (insulin, RNase). Unlike Hb or native albumin, globin and denatured albumin stimulated ATP hydrolysis and were substrates for proteolysis. The stimulation of ATP hydrolysis by potential substrates triggers activation of the proteolytic function.