Metarhodopsin-II stabilization by crosslinked Gtalpha C-terminal peptides and implications for the mechanism of GPCR-G protein coupling.
Metarhodopsin-II is the light-excited form of rhodopsin that triggers G protein function. Metarhodopsin-II is stabilized when the N-terminus of the carboxyl (340-350) tail peptide of the alpha-subunit of transducin (Gtalpha) is crosslinked to rhodopsin cysteine 140 or the 340-350 peptide C-terminus of Gtalpha is crosslinked to rhodopsin cysteine 316. When the N-terminus of the peptide is coupled to C316 the MI<-->MII equilibrium is not affected. The evidence suggests that the N-terminus of the 340-350 region of Gtalpha is located near C140 when transducin stabilizes metarhodopsin-II and alternative explanations are suggested for the effectiveness of the 340-350 Gtalpha tail peptide when bound to C316.
Angel
Thomas E
TE
Department of Microbiology, Montana State University, Bozeman, MT 59717, USA.
Kraft
Paul C
PC
Dratz
Edward A
EA
D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents; D003545:Cysteine / Q000378:metabolism; D003623:Dark Adaptation; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D013057:Spectrum Analysis
D003432:Cross-Linking Reagents; D044385:GTP-Binding Protein alpha Subunits; D010446:Peptide Fragments; D043562:Receptors, G-Protein-Coupled; C013110:metarhodopsins; D012243:Rhodopsin; D003545:Cysteine