title: A novel mode of sensory transduction in archaea: binding protein-mediated chemotaxis towards osmoprotectants and amino acids.
abstract: Directly upstream of the Halobacterium salinarum transducer genes basT and htpIV we identified two open reading frames (orfs) with significant homologies to genes encoding binding proteins for amino acids and compatible solutes, respectively. Behavioral testing of deletion mutants indicates that halobacterial chemotaxis towards branched-chain amino acids as well as compatible osmolytes of the betaine family requires both a binding and a transducer protein. We therefore named the binding/transducer proteins BasB/BasT for branched-chain and sulfur-containing amino acids and CosB/CosT for compatible solutes. Our data support a signaling mechanism with the binding proteins functioning as lipid-anchored receptors interacting with the extracellular domain of their cognate transducers. Inspection of the halobacterial genome suggests that BasB and CosB exclusively mediate chemotaxis responses without any additional role in transport, which is in contrast to bacterial binding proteins, which are always part of ABC transport systems. The CosB/CosT system is the first instance of a chemotaxis signaling pathway for organic osmolytes in the living world and natural abundance 13C-NMR analysis of cytoplasmic extracts suggests that H.salinarum utilizes these solutes for osmotic adaptation.
authors: Max-Planck Institut für Biochemie, D-82152 Martinsried, Germany.
authors: Maia V
authors: MV
authors: Kokoeva
authors: Kai-Florian
authors: KF
authors: Storch
authors: Christian
authors: C
authors: Klein
authors: Dieter
authors: D
authors: Oesterhelt
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000494:pharmacology*; D001105:Archaea / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics; D020745:Genome, Archaeal; D019617:Halobacterium salinarum / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016366:Open Reading Frames / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D000596:Amino Acids