title: Rhodopsin, Gq and phospholipase C activation in cephalopod photoreceptors.
abstract: We present characterization of the rhodopsin, Gq and phosphatidylinositol-specific phospholipase C (PLC) from the signal transduction pathway of cephalopod photoreceptors. Cephalopod rhodopsins are unique in possessing a C-terminal extension of proline-rich repeats, and they have a strong tendency to form ordered arrays. Two-dimensional arrays of a full-length and C-terminally-truncated cephalopod rhodopsin have been obtained. The C termini appear to cluster the rhodopsins into small groups. An AlF4(-)-activated Gq alpha subunit has been isolated and shown to activate a partially purified PLC beta. This 130 kDa PLC, isolated by absorption on heparin agarose, showed a specific activity of 195 nmol of phosphatidylinositol 4,5-bisphosphate hydrolysed per milligram of protein per minute in the presence of 1.6 microM free calcium.
authors.affiliation: Department of Crystallography, Birkbeck College, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Bhatia
authors.forename: A
authors.initials: A
authors.lastname: Davies
authors.forename: J B
authors.initials: JB
authors.lastname: Gaudoin
authors.forename: H R
authors.initials: HR
authors.lastname: Saibil
mesh_terms: D000818:Animals; D049832:Decapodiformes / Q000378:metabolism; D008974:Mollusca / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D010738:Type C Phospholipases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D012243:Rhodopsin; D010738:Type C Phospholipases