Edited by Donald L. D. Caspar, Florida State University, Tallahassee, FL, and approved March 18, 2008 (received for review January 11, 2008)
Rotation of the sodium-driven polar flagellum of Vibrio alginolyticus requires four motor proteins: PomA, PomB, MotX, and MotY. PomA and PomB form a sodium-ion channel in the cytoplasmic membrane that functions as a stator complex to couple sodium-ion flux with torque generation. MotX and MotY are components of the T-ring, which is located beneath the P-ring of the polar flagellar basal body and is involved in incorporation of the PomA/PomB complex into the motor. Here, we describe the determination of the crystal structure of MotY at 2.9 Å resolution. The structure shows two distinct domains: an N-terminal domain (MotY-N) and a C-terminal domain (MotY-C). MotY-N has a unique structure. MotY-C contains a putative peptidoglycan-binding motif that is remarkably similar to those of peptidoglycan-binding proteins, such as Pal and RmpM, but this region is disordered in MotY. Motility assay of cells producing either of the MotY-N and MotY-C fragments and subsequent biochemical analyses indicate that MotY-N is essential for association of the stator units around the rotor, whereas MotY-C stabilizes the association by binding to the peptidoglycan layer. Based on these observations, we propose a model for the mechanism of stator assembly around the rotor.
Author contributions: S.K. and A.S. contributed equally to this work; M.H., K.N., and K.I. designed research; S.K., A.S., H.T., T.Y., M.S., and K.I. performed research; S.K., A.S., H.T., and K.I. analyzed data; and S.K., A.S., and K.I. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The atomic coordinates have been deposited in Protein Data Bank, www.pdb.org (PDB ID code 2ZF8).
This article contains supporting information online at www.pnas.org/cgi/content/full/0800308105/DCSupplemental.
