Conformational coupling between receptor and kinase binding sites through a conserved salt bridge in a signaling complex scaffold protein.
Bacterial chemotaxis is one of the best studied signal transduction pathways. CheW is a scaffold protein that mediates the association of the chemoreceptors and the CheA kinase in a ternary signaling complex. The effects of replacing conserved Arg62 of CheW with other residues suggested that the scaffold protein plays a more complex role than simply binding its partner proteins. Although R62A CheW had essentially the same affinity for chemoreceptors and CheA, cells expressing the mutant protein are impaired in chemotaxis. Using a combination of molecular dynamics simulations (MD), NMR spectroscopy, and circular dichroism (CD), we addressed the role of Arg62. Here we show that Arg62 forms a salt bridge with another highly conserved residue, Glu38. Although this interaction is unimportant for overall protein stability, it is essential to maintain the correct alignment of the chemoreceptor and kinase binding sites of CheW. Computational and experimental data suggest that the role of the salt bridge in maintaining the alignment of the two partner binding sites is fundamental to the function of the signaling complex but not to its assembly. We conclude that a key feature of CheW is to maintain the specific geometry between the two interaction sites required for its function as a scaffold.
Joint Institute for Computational Sciences, University of Tennessee - Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Department of Physics, University of Tennessee, Knoxville, Tennessee, United States of America.
Davi R
DR
Ortega
Guoya
G
Mo
Kwangwoon
K
Lee
Hongjun
H
Zhou
Jerome
J
Baudry
Frederick W
FW
Dahlquist
Igor B
IB
Zhulin
D001665:Binding Sites; D002633:Chemotaxis; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D009154:Mutation; D011487:Protein Conformation; D058767:Protein Unfolding; D015203:Reproducibility of Results
C489103:CheW protein, E coli; D029968:Escherichia coli Proteins