title: Different conformations of the kinase-on and kinase-off signaling states in the Aer HAMP domain.
abstract: HAMP domains are sensory transduction modules that connect input and output domains in diverse signaling proteins from archaea, bacteria, and lower eukaryotes. Here, we employed in vivo disulfide cross-linking to explore the structure of the HAMP domain in the Escherichia coli aerotaxis receptor Aer. Using an Aer HAMP model based on the structure of Archaeoglobus 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-linked in 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.
authors.affiliation: Division of Microbiology and Molecular Genetics, Loma Linda University, Loma Linda, CA 92350, USA.
authors.forename: Kylie J
authors.initials: KJ
authors.lastname: Watts
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.forename: Barry L
authors.initials: BL
authors.lastname: Taylor
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019611:Archaeoglobus fulgidus / Q000235:genetics / Q000378:metabolism*; D019848:Gene Expression Regulation, Archaeal / Q000502:physiology*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D019843:Archaeal Proteins