Calcium-dependent assembly of centrin-G-protein complex in photoreceptor cells.
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.
Pulvermüller
Alexander
A
Institut für Medizinische Physik und Biophysik, Humboldt-Universität zu Berlin, Germany. alexander.pulvermueller@charite.de
Giessl
Andreas
A
Heck
Martin
M
Wottrich
Ralf
R
Schmitt
Angelika
A
Ernst
Oliver Peter
OP
Choe
Hui-Woog
HW
Hofmann
Klaus Peter
KP
Wolfrum
Uwe
U
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
D002135:Calcium-Binding Proteins; D002868:Chromosomal Proteins, Non-Histone; D046911:Macromolecular Substances; C056608:caltractin; D020962:Heterotrimeric GTP-Binding Proteins; D015293:Transducin; D002118:Calcium