Specific Isoprenyl Group Linked to Transducin -Subunit Is a Determinant of Its Unique Signaling Properties among G-Proteins

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• 作者：Takahiko Matsuda ; Yuichi Hashimoto ; Hiroshi Ueda ; Tomiko Asano ; Yoshiharu Matsuura ; Tomoko Doi ; Toshifumi Takao ; Yasutsugu Shimonishi ; and Yoshitaka Fukada
• 刊名：Biochemistry
• 出版年：1998
• 出版时间：July 7, 1998
• 年：1998
• 卷：37
• 期：27
• 页码：9843 - 9850
• 全文大小：194K
• 年卷期：v.37,no.27(July 7, 1998)
• ISSN：1520-4995

文摘

Among 11 subtypes of heterotrimeric G-protein -subunit,₁ (rod), ₈ (cone) and ₁₁aremodified with farnesyl while the others are modified withgeranylgeranyl at the C-terminus. To understandthe role of specific isoprenylation (farnesylation) of retinaltransducin, we examined how and to whatextent the type of isoprenyl group affects transducin-(₁₁) functions such as interactionswithmembranes, G/receptor, and effectors. To this end, theC-terminal farnesylation signal sequence (CVIS)of ₁ was replaced by a geranylgeranylation signal(CVIL), and the resultant mutant (S74L) or wild-type(WT) ₁ was coexpressed with ₁ in thebaculovirus-Tn5 insect cell system. Both ₁WT and₁S74Lexpressed as a complex were mixtures modified with farnesyl andgeranylgeranyl groups. The ratioof farnesyl to geranylgeranyl in preparations of₁₁WT and₁₁S74L purified from the Tn5 cellmembranefraction was about 1:2 and 1:6, respectively. These two forms ofrecombinant ₁₁ and retinal₁₁ weredifferent in their abilities to associate with rod outer segmentmembranes with the following rank order:₁₁S74L >₁₁WT > retinal₁₁. Functionally,₁₁S74L was the most potent topromote pertussistoxin-catalyzed ADP ribosylation of transducin- (T), to stimulatemetarhodopsin II-catalyzed GTPS-binding reaction to T and to modulate adenylyl cyclase andphospholipase C activities. All of the₁₁functions absolutely required the isoprenylation of the -subunit.As for the interaction with Go andadenylyl cyclase, predominantly geranylgeranylated₁₁S74L was less effective thangeranylgeranylated₁₂ purified from bovine brain. Theseresults demonstrate that the properties of G are stronglyaffectedby the type of functionally indispensable isoprenylation in addition tothe amino acid sequence of G.The relative contribution of the two factors depends on proteinswith which G interacts.