Resume

• 2006

  Imperial College London

  UC Berkeley

  Purification

  crystallization

  reconstitution and electron microscopy characterization of membrane proteins.

  Imperial College London

  Assistant Professor

  Bryan/College Station

  Texas Area

  Department of Biology

  Texas A&M University

  American Society of Microbiology

• 2002

  Peking University

  Department of Biology

  Texas A&M University

  Structural and genetic analysis of the mechanism of transmembrane signal transduction in two-component systems

  microarray studies in multiple bacterial systems

  protein engineering and mutagenesis.

  Peking University

  Postdoctoral Fellow

  Department of Molecular and Cell Biology

  UC Berkeley

  UC Berkeley

  Berkeley

  California

  Utilize super-resolution microscopy

  biochemical

  molecular biology techniques and project management skills to execute an independent research project on the mechanism and regulation in bacterial locomotion.

  Associate specialist

  Chinese

  English

  Ph. D

  Biochemistry and Molecular Biology

• SDS-PAGE

  Protein Chemistry

  Microscopy

  Western Blotting

  Protein Purification

  Cell Culture

  X-ray crystallography

  Bioinformatics

  Immunofluorescence

  Confocal Microscopy

  Molecular Biology

  PCR

  Molecular Cloning

  Cell Biology

  Protein Expression

  Biophysics

  Biochemistry

  RT-PCR

  Genetics

  Fluorescence Microscopy

  From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution

  Wen

  J.

  Zhang

  L.

  Liu

  J

  Liu

  X.

  Sinorhizobium meliloti DctB is a typical transmembrane sensory histidine kinase

  which senses C4-dicarboxylic acids (DCA) and regulates the expression of DctA

  the DCA transporter. We previously reported the crystal structures of its periplasmic sensory domain (DctBp) in apo and succinate-bound states

  and these structures showed dramatic conformational changes at dimeric level. Here we show a ligand-induced dimeric switch in solution and a strong correlation between DctBp's dimerization states and the in vivo activities of DctB. Using site-directed mutagenesis

  we identify important determinants for signal perception and transduction. Specifically

  we show that the ligand-binding pocket is essential for DCA-induced ‘on’ activity of DctB. Mutations at different sections of DctBp's dimerization interface can lock full-length DctB at either ‘on’ or ‘off’ state

  independent of ligand binding. Taken together

  these results suggest that DctBp's signal perception and transduction occur through a ‘ligand-induced dimeric switch’

  in which the changes in the dimeric conformations upon ligand binding are responsible for the signal transduction in DctB.

  From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution

  Neu

  J. C.

  Chen

  J.

  Myxococcus xanthus is a Gram-negative bacterium that glides over surfaces without the aid of flagella. Two motility systems are used for locomotion: social-motility

  powered by the retraction of type IV pili

  and adventurous (A)-motility

  powered by unknown mechanism(s). We have shown that AgmU

  an A-motility protein

  is part of a multiprotein complex that spans the inner membrane and periplasm of M. xanthus. In this paper

  we present evidence that periplasmic 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 homologs. 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.

  Myxobacteria gliding motility requires cytoskeleton rotation powered by proton motive force.

  Bacterial gliding motility is the smooth movement of cells on solid surfaces unaided by flagella or pili. Many diverse groups of bacteria exhibit gliding

  but the mechanism of gliding motility has remained a mystery since it was first observed more than a century ago. Recent studies on the motility of Myxococcus xanthus

  a soil myxobacterium

  suggest a likely mechanism for gliding in this organism. About forty M. xanthus genes were shown to be involved in gliding motility

  and some of their protein products were labeled and localized within cells. These studies suggest that gliding motility in M. xanthus involves large multiprotein structural complexes

  regulatory proteins

  and cytoskeletal filaments. In this review

  we summarize recent experiments that provide the basis for this emerging view of M. xanthus motility. We also discuss alternative models for gliding.

  Uncovering the mystery of gliding motility in myxobacteria

  Zusman

  D. R.

  Yildiz

  A.

  Sun

  I.-H.

  Moghtaderi

  A.

  Bandaria

  J. N.

  Gliding is a form of enigmatic bacterial surface motility that does not use visible external structures such as flagella or pili. This study characterizes the single-molecule dynamics of the Myxococcus xanthus gliding motor protein AglR

  a homolog of the Escherichia coli flagella stator protein MotA. However

  the Myxococcus motors

  unlike flagella stators

  lack peptidoglycan-binding domains. With photoactivatable localization microscopy (PALM)

  we found that these motor proteins move actively within the cell membrane and generate torque by accumulating in clusters that exert force on the gliding surface. Our model unifies gliding and swimming with conserved power-generating modules.

  Flagella stator homologs function as motors for myxobacterial gliding motility by moving in helical trajectories

  Chen

  J.

  McBride

  M. J.

  Many bacteria glide smoothly on surfaces

  but with no discernable propulsive organelles on their surface. Recent experiments with Myxococcus xanthus and Flavobacterium johnsoniae show that both distantly related bacterial species glide utilizing proteins that move in helical tracks

  albeit with significantly different motility mechanisms. Both species utilize proton motive force for movement. However

  the motors that power gliding in M. xanthus have been identified

  while the F. johnsoniae motors remain to be discovered.

  Bacteria that glide with helical tracks

  A multi-protein complex from Myxococcus xanthus required for bacterial gliding motility.

  Wang

  A.

  Sun

  I.-H.

  Mauriello

  E. M. F.

  Myxococcus xanthus moves by gliding motility powered by Type IV pili (S-motility) and a second motility system

  A-motility

  whose mechanism remains elusive despite the identification of ∼40 A-motility genes. In this study

  we used biochemistry and cell biology analyses to identify multi-protein complexes associated with A-motility. Previously

  we showed that the N-terminal domain of FrzCD

  the receptor for the frizzy chemosensory pathway

  interacts with two A-motility proteins

  AglZ and AgmU. Here we characterized AgmU

  a protein that localized to both the periplasm and cytoplasm. On firm surfaces

  AgmU-mCherry colocalized with AglZ as distributed clusters that remained fixed with respect to the substratum as cells moved forward. Cluster formation was favoured by hard surfaces where A-motility is favoured. In contrast

  AgmU-mCherry clusters were not observed on soft agar surfaces or when cells were in large groups

  conditions that favour S-motility. Using glutathione-S-transferase affinity chromatography

  AgmU was found to interact either directly or indirectly with multiple A-motility proteins including AglZ

  AglT

  AgmK

  AgmX

  AglW and CglB. These proteins

  important for the correct localization of AgmU and AglZ

  appear to be organized as a motility complex

  spanning the cytoplasm

  inner membrane and the periplasm. Identification of this complex may be important for uncovering the mechanism of A-motility.

  A multi-protein complex from Myxococcus xanthus required for bacterial gliding motility.

  Nan

  Department of Molecular and Cell Biology

  UC Berkeley