Yoo S J, Seol J H, Kang M S, Chung C H
Department of Molecular Biology, College of Natural Sciences, Seoul National University, Korea.
Biochem Biophys Res Commun. 1996 Dec 13;229(2):531-5. doi: 10.1006/bbrc.1996.1838.
Hs1VU in E. coli is a new type of ATP-dependent protease composed of two heat shock proteins, the HslU ATPase and the HslV peptidase related to certain beta-type subunits of the 20S proteasome. Here we show that the ATP-dependent hydrolysis of N-carbobenzoxy-Gly-Gly-Leu-7-amido-4-methylcoumarin by the HslVU protease can be markedly stimulated by poly-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 the ATPase activity of HslU also increased the rate of the ATP-dependent peptide hydrolysis by HslV, although to a much lesser extent than by poly-L-lysine. Thus, the poly-L-lysine-mediated increase in the ATPase activity of HslU appears to be responsible for the dramatic activation of the ATP-dependent peptide hydrolysis by HslV. These results suggest that, in the reconstituted HslVU complex, the peptide hydrolysis by HslV occurs in a tightly coupled process with the cleavage of ATP by HslU.
大肠杆菌中的Hs1VU是一种新型的ATP依赖性蛋白酶，由两种热休克蛋白组成，即HslU ATP酶和与20S蛋白酶体某些β型亚基相关的HslV肽酶。我们在此表明，HslVU蛋白酶对N-苄氧羰基-甘氨酰-甘氨酰-亮氨酸-7-氨基-4-甲基香豆素的ATP依赖性水解可被聚-L-赖氨酸显著刺激，聚-L-赖氨酸已知可激活20S蛋白酶体的酪蛋白降解活性。然而，聚-L-赖氨酸对HslV自身的肽酶活性几乎没有影响。相反，它使HslU的ATP水解增加了几倍。能够刺激HslU ATP酶活性的组蛋白也提高了HslV对ATP依赖性肽水解的速率，尽管程度远低于聚-L-赖氨酸。因此，聚-L-赖氨酸介导的HslU ATP酶活性增加似乎是HslV对ATP依赖性肽水解产生显著激活作用的原因。这些结果表明，在重组的HslVU复合物中，HslV的肽水解与HslU对ATP的裂解以紧密偶联的过程发生。
