Rhodopsin, Gq and phospholipase C activation in cephalopod photoreceptors.
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.
Bhatia
J
J
Department of Crystallography, Birkbeck College, London, UK.
Davies
A
A
Gaudoin
J B
JB
Saibil
H R
HR
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*
D012243:Rhodopsin; D010738:Type C Phospholipases