Analysis of the Cooperative ATPase Cycle of the AAA plus Chaperone ClpB from Thermus thermophilus by Using Ordered Heterohexamers with an Alternating Subunit Arrangement

作者：Yamasaki Takashi; Oohata Yukiko; Nakamura Toshiki; Watanabe Yo hei^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2015, 290(15): 9789-9800.

DOI：10.1074/jbc.M114.617696

The ClpB/Hsp104 chaperone solubilizes and reactivates protein aggregates in cooperation with llnaK/Hsp70 and its cofactors. The CIpB/Hsp104 protomer has two AAA+ modules, AAA-1 and AAA-2, and forms a homohexamer. In the hexamer, these modules form a two-tiered ring in which each tier consists of homotypic AAA+ modules. By ATP binding and its hydrolysis at these AAA+ modules, ClpB/Hsp104 exerts the mechanical power required for protein disaggregation. Although ATPase cycle of this chaperone has been studied by several groups, an integrated understanding of this cycle has not been obtained because of the complexity of the mechanism and differences between species. To improve our understanding of the ATPase cycle, we prepared many ordered heterohexamers of ClpB from Thermus thermophilus, in which two subunits having different mutations were cross-linked to each other and arranged alternately and measured their nucleotide binding, ATP hydrolysis, and disaggregation abilities. The results indicated that the AT Pase cycle of ClpB proceeded as follows: (i) the 12 AAA+ modules randomly bound ATP, (ii) the binding of four or more ATP to one AAA+ ring was sensed by a conserved Arg residue and converted another AAA+ ring into the ATPase-active form, and (iii) ATP hydrolysis occurred cooperatively in each ring. We also found that cooperative ATP hydrolysis in at least one ring was needed for the disaggregation activity of ClpB.

• 出版日期2015-4-10