Beiyan Nan, Ph.D
Myxococcus xanthus is a Gram-negative bacterium that glides over surfaces without the aid of flagella. Two motility systems are used for locomotion: twitch motility, powered by the retraction of Type IV pili, and gliding motility, powered by unknown mechanism(s). Our studies have shown that AgmU, an A-motility protein, is part of a multi-protein complex that spans the cytoplasm, inner membrane and periplasm of M. xanthus. Further investigation revealed that one subpopulation of AgmU decorates a looped continuous helix that rotates clockwise as cells glide forward, reversing its rotation when cells reverse polarity. Inhibitor studies showed that the AgmU helix rotation is driven by proton motive force (PMF) and depends on actin-like MreB cytoskeletal filaments. The AgmU motility complex was found to interact with MotAB homologues. Our data are consistent with a mechanochemical model in which PMF-driven motors, similar to bacterial flagella stator complexes, run along an endless looped helical track, driving rotation of the track; deformation of the cell surface by the AgmU associated proteins creates pressure waves in the slime, pushing cells forward. My current studies focus on the composition and regulation of the gliding engines.
1. Nan, B., Chen, J., Neu, J. C., Berry, R. M., Oster, G. and Zusman, D. R. (2011) Myxobacteria gliding motility requires cytoskeleton rotation powered by proton motive force. PNAS 108: 2498-2503. (Highlighted article)
2. (Review) Nan, B. and Zusman, D. R. (2011) Uncovering the mystery of gliding motility in myxobacteria. Annu. Rev. Genet. 45: 21-39.
3. Nan, B., Mauriello, E. M. F., Sun, I., Wong, A. and Zusman, D. R. (2010) A multi-protein complex from Myxococcus xanthus required for bacterial gliding motility. Mol. Microbiol. 76: 1539-1554.
4. Nan, B., Liu, X., Zhou, Y., Liu, J., Zhang, L., Wen, J., Zhang, X., Su, X. and Wang, Y. (2010) From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution. Mol. Microbiol. 75:1484-1494. (One of the 16 selected papers presented in the first Mol Micro Meeting Würzburg (M3W) in May 2011, Germany)
5. Zhou, Y., Nan, B., Nan, J., Ma, Q., Panjikar, S., Liang, Y., Wang, Y. and Su, X.  (2008) C4-dicarboxylates sensing mechanism revealed by the crystal structures of DctB sensor domain. J. Mol. Biol. 383: 49-61 (Joint first author).
6. Nan, B., Zhou, Y., Liang, Y., Wen, J., Ma, Q., Zhang, S., Wang, Y. and Su, X. (2006) Purification and preliminary X-ray crystallographic analysis of the ligand-binding domain of Sinorhizobium meliloti DctB. Biochim. Biophys. Acta. 1764: 839-841.
7. Mauriello, E. M. F., Mouhamar, F., Nan, B., Ducret, A., Dai, D., Zusman, D. R. and Mignot, T. (2010) Bacterial motility complexes require the actin-like protein, MreB and the Ras homologue, MglA. EMBO J. 29: 315-326.
8. Mauriello, E. M. F., Nan, B. and Zusman, D. R. (2009) AglZ regulates adventurous (A-) motility in Myxococcus xanthus through its interaction with the cytoplasmic receptor, FrzCD. Mol. Microbiol. 72: 964-977.
9. Cui, G., Nan, B., Hu, J., Wang, Y., Jin, C. and Xia, B. (2006) Identification and solution structures of a single-domain biotin/lipoyl attachment protein from Bacillus subtilis. J. Biol. Chem. 281: 20598-20607.
10. Huo, Y., Nan, B., You, C., Tian, Z., Kolb, A. and Wang, Y. (2006) FIS activates glnAp2: role of a DNA bend centered at -55, upstream of the transcription start site. FEMS Microbiol. Lett. 257: 99-105.