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Structural basis of FliG – FliM interaction in H elicobacter pylori
Author(s) -
Lam KwokHo,
Lam Wendy Wai Ling,
Wong Jase YanKit,
Chan LingChim,
Kotaka Masayo,
Ling Thomas KinWah,
Jin DongYan,
Ottemann Karen M.,
Au Shan WingNgor
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12222
Subject(s) - biology , biophysics , biochemistry
Summary FliG and FliM are switch proteins that regulate the rotation and switching of the flagellar motor. Several assembly models for FliG and FliM have recently been proposed; however, it remains unclear whether the assembly of the switch proteins is conserved among different bacterial species. We applied a combination of pull‐down, thermodynamic and structural analyses to characterize the FliM – FliG association from the mesophilic bacterium H elicobacter pylori. FliM binds to FliG with micromolar binding affinity, and their interaction is mediated through the middle domain of FliG ( FliG M ), which contains the EHPQR motif. Crystal structures of the middle domain of H . pylori FliM ( FliM M ) and FliG M – FliM M complex revealed that FliG binding triggered a conformational change of the FliM α3‐α1′ loop, especially Asp 130 and Arg 144. We furthermore showed that various highly conserved residues in this region are required for FliM – FliG complex formation. Although the FliM – FliG complex structure displayed a conserved binding mode when compared with T hermotoga maritima , variable residues were identified that may contribute to differential binding affinities across bacterial species. Comparison of the thermodynamic parameters of FliG – FliM interactions between H . pylori and E scherichia coli suggests that molecular basis and binding properties of FliM to FliG is likely different between these two species.