W. Vonderheide et al., INTERACTION OF GUANOSINE 5'-TRIPHOSPHATE BINDING-PROTEIN GQ FROM SEPIA-OFFICINALIS WITH ILLUMINATED RHODOPSIN BOUND TO CONCANAVALIN-A, Journal of photochemistry and photobiology.B, Biology, 35(1-2), 1996, pp. 25-31
The heterotrimeric guanosine 5'-triphosphate (GTP)-binding protein Gq
was suggested to couple the light receptor rhodopsin with the effector
phospholipase C in visual cells of invertebrates. We indirectly linke
d Gq from Sepia officinalis to a concanavalin A-sepharose column via r
hodopsin. Rhodopsin had been solubilized previously with 10 mM n-dodec
yl-beta-maltoside from the purified photosensory membrane under illumi
nation. All three subunits of the Gq were released almost pure by elut
ion with 100 mu M GTP. The alpha and beta subunits were identified by
specific antipeptide antisera. The alpha subunit has a relative molecu
lar mass of 46 kDa, and the beta subunit of 35 kDa. The gamma subunit
corresponds to a 9 kDa polypeptide owing to the molecular mass, which
is similar to the G(gamma) subunit of squid. The use of specific antib
odies shows that neither actin nor G-protein related to transducin wer
e in the fractions eluted with GTP or alpha-methyl mannoside. We demon
strate that all three subunits of Gq were associated with rhodopsin of
invertebrates. Such use of a lectin column might be useful for furthe
r investigations of the interaction of rhodopsin and Gq.