Rhodopsin/transducin interactions. II. Influence of the transducin-beta gamma subunit complex on the coupling of the transducin-alpha subunit to rhodopsin.

摘要: In these studies we have investigated the role of beta gamma T subunit complex in promoting rhodopsin-stimulated guanine nucleotide exchange reaction (i.e. activation event) alpha subunit. The results demonstrate that although increases association with lipid vesicles lack photoreceptor, is not necessary for binding to containing rhodopsin, provided sufficient amounts rhodopsin are present. rhodopsin-promoted GDP/guanosine 5'-O-(3-thiotriphosphate) (GTP S) reaction, within rhodopsin-alpha complex, then dissociation TGTP S species from rhodopsin-containing phospholipid vesicles. A second line evidence occurrence rhodopsin/alpha interactions, absence T, comes phosphorylation using 1 isoform protein kinase C. by C inhibited both and presence but enhanced T. These complexes also appear be capable undergoing a event. When allowed occur prior addition C, inhibited. Although absolutely required interaction, it appears increase apparent affinity when was inserted into phosphatidylcholine soluble lipid-free preparations were used. This significant kinetic advantage event, such causes 10-fold promotion rhodopsin-stimulation [35S]GTP after min provides less than 20% h. ability vesicle surface does contribute significantly couple functionally subunits, there no requirement once has formed.