Publication Type:Journal Article
Source:Journal of Molecular Biology, Volume 330, Number 2, p.185-195 (2003)
Keywords:hsluv (h. influenzae); clp/hsp100 proteins; aaa proteins; proteasome; vinyl sulfone; atp-dependent protease; escherichia-coli homolog; cell-division inhibitor; electron-density maps; crystal-structure; 20s proteasome; proteolytic activity; beta-subunits;
In the prokaryotic homolog of the eukaryotic proteasome, HslUV, the "double donut" HsIV protease is allosterically activated by Hs1U, an AAA protein of the Clp/Hsp100 family consisting of three (amino-terminal, carboxy-terminal, and intermediate) domains. The intermediate domains of HslU, which extend like tentacles from the hexameric ring formed by the amino-terminal and carboxy-terminal domains, have been deleted; an asymmetric Hs1U(DeltaI)(6)Hs1V(12) complex has been crystallized; and the structure has been solved to 2.5 Angstrom resolution, revealing an assembly in which a Hs1U(DeltaI) hexamer binds one end of the Hs1V dodecamer. The conformation of the protomers of the HsQU(DeltaI)-complexed Hs1V hexamer is similar to that in the symmetric wild-type Hs1UV complex, while the protomer conformation of the uncomplexed HsIV hexamer is similar to that of HsIV alone. Reaction in the crystals with a vinyl sulfone inhibitor reveals that the Hs1U(DeltaI)-complexed Hs1V hexamer is active, while the uncomplexed Hs1V hexamer is inactive. These results confirm that HsIV can be activated by binding of a hexameric Hs1U(DeltaI), ring lacking the I domains, that activation is effected through a conformational change in Hs1V rather than through alteration of the size of the entry channel into the protease catalytic cavity, and that the two HS1V(6) rings in the protease dodecamer are activated independently rather than cooperatively. (C) 2003 Elsevier Science Ltd. All rights reserved.