Functional similarities among two-component sensors and methyl-accepting chemotaxis proteins suggest a role for linker region amphipathic helices in transmembrane signal transduction.
Signal-responsive components of transmembrane signal-transducing regulatory systems include methyl-accepting chemotaxis proteins and membrane-bound, two-component histidine kinases. Prokaryotes use these regulatory networks to channel environmental cues into adaptive responses. A typical network is highly discriminating, using a specific phosphoryl relay that connects particular signals to appropriate responses. Current understanding of transmembrane signal transduction includes periplasmic signal binding with the subsequent conformational changes being transduced, via transmembrane helix movements, into the sensory protein's cytoplasmic domain. These induced conformational changes bias the protein's regulatory function. Although the mutational analyses reviewed here identify a role for the linker region in transmembrane signal transduction, no specific mechanism of linker function has yet been described. We propose a speculative, mechanistic model for linker function based on interactions between two putative amphipathic helices. The model attempts to explain both mutant phenotypes and hybrid sensor data, while accounting for recognized features of amphipathic helices.
Williams
S B
SB
Department of Biology, Texas A & M University, College Station, TX 77843-3258, USA. stan@mail.bio.tamu.edu
Stewart
V
V
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D002633:Chemotaxis / Q000502:physiology*; D000071677:Histidine Kinase; D008566:Membranes / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011494:Protein Kinases / Q000737:chemistry / Q000502:physiology*; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*
D001426:Bacterial Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase