title: Calcium-dependent assembly of centrin-G-protein complex in photoreceptor cells.
abstract: Photoexcitation of rhodopsin activates a heterotrimeric G-protein cascade leading to cyclic GMP hydrolysis in vertebrate photoreceptors. Light-induced exchanges of the visual G-protein transducin between the outer and inner segment of rod photoreceptors occur through the narrow connecting cilium. Here we demonstrate that transducin colocalizes with the Ca(2+)-binding protein centrin 1 in a specific domain of this cilium. Coimmunoprecipitation, centrifugation, centrin overlay, size exclusion chromatography, and kinetic light-scattering experiments indicate that Ca(2+)-activated centrin 1 binds with high affinity and specificity to transducin. The assembly of centrin-G-protein complex is mediated by the betagamma-complex. The Ca(2+)-dependent assembly of a G protein with centrin is a novel aspect of the supply of signaling proteins in sensory cells and a potential link between molecular translocations and signal transduction in general.
authors.affiliation: Institut für Medizinische Physik und Biophysik, Humboldt-Universität zu Berlin, Germany. alexander.pulvermueller@charite.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Pulvermüller
authors.forename: Andreas
authors.initials: A
authors.lastname: Giessl
authors.forename: Martin
authors.initials: M
authors.lastname: Heck
authors.forename: Ralf
authors.initials: R
authors.lastname: Wottrich
authors.forename: Angelika
authors.initials: A
authors.lastname: Schmitt
authors.forename: Oliver Peter
authors.initials: OP
authors.lastname: Ernst
authors.forename: Hui-Woog
authors.initials: HW
authors.lastname: Choe
authors.forename: Klaus Peter
authors.initials: KP
authors.lastname: Hofmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfrum
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D002498:Centrifugation; D002850:Chromatography, Gel; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D008027:Light; D046911:Macromolecular Substances; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D008970:Molecular Weight; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D011233:Precipitin Tests; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D012542:Scattering, Radiation; D015398:Signal Transduction; D013379:Substrate Specificity; D015293:Transducin / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D002868:Chromosomal Proteins, Non-Histone; D046911:Macromolecular Substances; C056608:caltractin; D020962:Heterotrimeric GTP-Binding Proteins; D015293:Transducin; D002118:Calcium