The HslU ATPase acts as a molecular chaperone in prevention of aggregation of SulA, an inhibitor of cell division in Escherichia coli.
HslVU is an ATP-dependent protease consisting of two multimeric components: the HslU ATPase and the HslV peptidase. SulA, which is an inhibitor of cell division and has high tendency of aggregation, is degraded by HslVU protease. Here we show that HslU plays a role not only as a regulatory component for the HslV-mediated proteolysis but also as a molecular chaperone. Purified HslU prevented aggregation of SulA in a concentration-dependent fashion. This chaperone activity required oligomerization of HslU subunits, which could be achieved by ATP-binding or in the presence of high HslU protein concentrations. hsl mutation reduced the SulA-mediated inhibition of cell growth and this effect could be reversed upon overproduction of HslU, suggesting that HslU promotes the ability of SulA to block cell growth through its chaperone function. Thus, HslU appears to have two antagonistic functions: one as a chaperone for promotion of the ability of SulA in cell growth inhibition by preventing SulA aggregation and the other as the regulatory component for elimination of SulA by supporting the HslV-mediated degradation.
Seong
I S
IS
School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-742, South Korea.
Oh
J Y
JY
Lee
J W
JW
Tanaka
K
K
Chung
C H
CH
D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism* / Q000502:physiology; D001704:Biopolymers; D002455:Cell Division / Q000502:physiology*; D003598:Cytoskeletal Proteins; D010450:Endopeptidases / Q000378:metabolism*; D004926:Escherichia coli / Q000166:cytology*; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D011485:Protein Binding; D012697:Serine Endopeptidases
D001426:Bacterial Proteins; D001704:Biopolymers; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C053139:sulA protein, E coli; D010450:Endopeptidases; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; D000251:Adenosine Triphosphatases