Published:
Proceedings of the National Academy of Sciences, 2007
Published in:
Proceedings of the National Academy of Sciences, 104 (2007) 2, Seite 485-490
Language:
English
DOI:
10.1073/pnas.0608090104
ISSN:
1091-6490;
0027-8424
Origination:
Footnote:
Description:
Construction of the bacterial flagellum in the cell exterior proceeds at its distal end by highly ordered self-assembly of many different component proteins, which are selectively exported through the central channel of the growing flagellum by the flagellar type III export apparatus. FliI is the ATPase of the export apparatus that drives the export process. Here we report the 2.4 Å resolution crystal structure of FliI in the ADP-bound form. FliI consists of three domains, and the whole structure shows extensive similarities to the α and β subunits of F 0 F 1 -ATPsynthase, a rotary motor that drives the chemical reaction of ATP synthesis. A hexamer model of FliI has been constructed based on the F 1 -ATPase structure composed of the α 3 β 3 γ subunits. Although the regions that differ in conformation between FliI and the F 1 -α/β subunits are all located on the outer surface of the hexamer ring, the main chain structures at the subunit interface and those surrounding the central channel of the ring are well conserved. These results imply an evolutionary relation between the flagellum and F 0 F 1 -ATPsynthase and a similarity in the mechanism between FliI and F 1 -ATPase despite the apparently different functions of these proteins.