Tuning a bacterial chemoreceptor with protein-membrane interactions.
Chemoreceptors in Escherichia coli are homodimeric transmembrane proteins that convert environmental stimuli into intracellular signals controlling flagellar motion. Chemoeffectors bind to the extracellular (periplasmic) domain of the receptors, whereas their cytoplasmic domain mediates signaling and adaptation. The second transmembrane helix (TM2) connects these two domains. TM2 contains an aliphatic core flanked by amphipathic aromatic residues that have specific affinity for polar-hydrophobic membrane interfaces. We previously showed that Trp-209, near the cytoplasmic end of TM2, helps maintain the normal baseline-signaling state of the aspartate chemoreceptor (Tar) and that Tyr-210 plays an auxiliary role in this control. We have now repositioned the Trp-209/Tyr-210 pair in single-residue increments about the cytoplasmic polar-hydrophobic interface. Changes from WY-2 to WY+1 modulate the baseline-signaling state of the receptor in predictable and incremental steps that can be compensated by adaptive methylation/demethylation. Greater displacements, as in WY-3, WY+2, and WY+3, bias the receptor to the off kinase-inhibiting state or the on kinase-stimulating state, respectively, to a degree that cannot be fully compensated by the adaptation system. Aromatic residues analogous to Trp-209/Tyr-210 are present in other chemoreceptors and many transmembrane sensor kinases, where they may serve a similar function.
Draheim
Roger R
RR
Department of Biology, 3258 TAMU, Texas A&M University, College Station, Texas 77843, USA.
Bormans
Arjan F
AF
Lai
Run-Zhi
RZ
Manson
Michael D
MD
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D001665:Binding Sites; D002628:Chemoreceptor Cells / Q000737:chemistry / Q000502:physiology*; D004926:Escherichia coli / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology; D008745:Methylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments; D011487:Protein Conformation
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D010446:Peptide Fragments