POLY-L-LYSINE ACTIVATES BOTH PEPTIDE AND ATP HYDROLYSIS BY THE ATP-DEPENDENT HSLVU PROTEASE IN ESCHERICHIA-COLI

HslVU in E. coli is a new type of ATP-dependent protease composed of t wo heat shock proteins, the HslU ATPase and the HslV peptidase related to certain beta-type subunits of the 20S proteasome. Here we show tha t the ATP-dependent hydrolysis of -carbobenzoxy-Gly-Gly-Leu-7-amido-4- methylcoumarin by the HslVU protease can be markedly stimulated by pol y-l-lysine, that is known to activate the casein-degrading activity of the 20S proteasome. However, poly-l-lysine showed little or no effect on the peptidase activity of HslV itself. Instead, it stimulated the hydrolysis of ATP by HslU several-fold. Histone that could stimulate t he ATPase activity of HslU also increased the rate of the ATP-dependen t peptide hydrolysis by HslV, although to a much lesser extent than by poly-l-lysine. Thus, the poly-l-lysine-mediated increase in the ATPas e activity of HslU appears to be responsible for the dramatic activati on of the ATP-dependent peptide hydrolysis by HslV. These results sugg est that, in the reconstituted HslVU complex, the peptide hydrolysis b y HslV occurs in a tightly coupled process with the cleavage of ATP by HslU. (C) 1996 Academic Press, Inc.