title: Role of the HAMP domain region of sensory rhodopsin transducers in signal transduction.
abstract: Archaea are able to sense light via the complexes of sensory rhodopsins I and II and their corresponding chemoreceptor-like transducers HtrI and HtrII. Though generation of the signal has been studied in detail, the mechanism of its propagation to the cytoplasm remains obscured. The cytoplasmic part of the transducer consists of adaptation and kinase activity modulating regions, connected to transmembrane helices via two HAMP (histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, phosphatases) domains. The inter-HAMP region of Natronomonas pharaonis HtrII (NpHtrII) was found to be α-helical [Hayashi, K., et al. (2007) Biochemistry 46, 14380-14390]. We studied the inter-HAMP regions of NpHtrII and other phototactic signal transducers by means of molecular dynamics. Their structure is found to be a bistable asymmetric coiled coil, in which the protomers are longitudinally shifted by ~1.3 Å. The free energy penalty for the symmetric structure is estimated to be 1.2-1.5 kcal/mol depending on the molarity of the solvent. Both flanking HAMP domains are mechanistically coupled to the inter-HAMP region and are asymmetric. The longitudinal shift in the inter-HAMP region is coupled with the in-plane displacement of the cytoplasmic part by 8.6 Å relative to the transmembrane part. The established properties suggest that (1) the signal may be transduced through the inter-HAMP domain switching and (2) the inter-HAMP region may allow cytoplasmic parts of the transducers to come sufficiently close to each other to form oligomers.
authors.affiliation: Research-educational Centre Bionanophysics, Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
authors.forename: Ivan Yu
authors.initials: IY
authors.lastname: Gushchin
authors.forename: Valentin I
authors.initials: VI
authors.lastname: Gordeliy
authors.forename: Sergei
authors.initials: S
authors.lastname: Grudinin
mesh_terms: D000262:Adenylyl Cyclases / Q000737:chemistry* / Q000502:physiology; D019843:Archaeal Proteins / Q000737:chemistry* / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism / Q000502:physiology; D006216:Halobacteriaceae / Q000201:enzymology / Q000378:metabolism*; D000071677:Histidine Kinase; D055537:Light Signal Transduction / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D000072236:Methyl-Accepting Chemotaxis Proteins; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000502:physiology; D011494:Protein Kinases / Q000737:chemistry* / Q000502:physiology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000502:physiology
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; C434451:HtrII protein, Natronobacterium pharaonis; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D021122:Protein Subunits; D025603:Sensory Rhodopsins; D011494:Protein Kinases; D000071677:Histidine Kinase; D010744:Phosphoric Monoester Hydrolases; D000262:Adenylyl Cyclases