Open AccessDifferent Conformations of the Kinase-On and Kinase-Off Signaling States in the Aer HAMP Domain
Author(s) -
Kylie J. Watts,
Mark S. Johnson,
Barry Taylor
Publication year - 2011
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01069-10
Subject(s) - hamp , hamp domain , helix bundle , biology , biochemistry , signal transduction , kinase , helix (gastropod) , bundle , microbiology and biotechnology , biophysics , protein structure , binding site , materials science , binding domain , ecology , immunology , hepcidin , snail , inflammation , composite material
HAMP domains are sensory transduction modules that connect input and output domains in diverse signaling proteins from archaea, bacteria, and lower eukaryotes. Here, we employedin vivo disulfide cross-linking to explore the structure of the HAMP domain in theEscherichia coli aerotaxis receptor Aer. Using an Aer HAMP model based on the structure ofArchaeoglobus fulgidus Af1503-HAMP, the closest residue pairs at the interface of the HAMP AS-1 and AS-2′ helices were determined and then replaced with cysteines and cross-linkedin vivo . Except for a unique discontinuity in AS-2, the data suggest that the Aer HAMP domain forms a parallel four-helix bundle that is similar to the structure of Af1503. The HAMP discontinuity was associated with a segment of AS-2 that was recently shown to interact with the Aer-PAS sensing domain. The four-helix HAMP bundle and its discontinuity were maintained in both the kinase-on and kinase-off states of Aer, although differences in the rates of disulfide formation also indicated the existence of different HAMP conformations in the kinase-on and kinase-off states. In particular, the kinase-on state was accompanied by significantly increased disulfide formation rates at the distal end of the HAMP four-helix bundle. This indicates that HAMP signaling may be associated with a tilting of the AS-1 and AS-2′ helices, which may be the signal that is transmitted to the kinase control region of Aer.