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G Protein Subtype Specificity of Rhodopsin Intermediates Metarhodopsin Ib and Metarhodopsin II
Author(s) -
Morizumi Takefumi,
Kimata Naoki,
Terakita Akihisa,
Imamoto Yasushi,
Yamashita Takahiro,
Shichida Yoshinori
Publication year - 2009
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2008.00396.x
Subject(s) - transducin , amino acid , rhodopsin , chemistry , stereochemistry , mutant , biochemistry , retinal , gene
Rhodopsin is one of the members of the G protein‐coupled receptor family that can catalyze a GDP–GTP exchange reaction on the retinal G protein transducin (Gt) upon photon absorption. There are at least two intermediate states, meta‐Ib and meta‐II, which exhibit direct interaction with Gt. Meta‐Ib binds to GDP‐bound Gt, while meta‐II forms a complex with Gt having no nucleotide, suggesting that meta‐Ib is a state that initially interacts with Gt. Here we investigated whether or not meta‐Ib exhibits specific interaction with G protein similar to meta‐II, by examining the binding efficiencies of meta‐Ib and meta‐II to Giα and its mutants whose C‐terminal 11 amino acids were replaced with those of Goα, Gqα and Gsα. The affinity of meta‐Ib to the C‐terminal 11 amino acids of Gtα was similar to those of Giα and its mutant with Goα’s C‐terminal 11 amino acids, whereas meta‐II exhibited affinity to the C‐terminal 11 amino acids of Giα mutant with Goα’s C‐terminal 11 amino acids about half of what was seen for Gtα and Giα. Both intermediates exhibited no affinity to the Giα mutants containing the C‐terminal 11 amino acids of Gqα and Gsα. These results suggested that meta‐Ib is the state that exhibits specific interaction with G protein as meta‐II does, although meta‐Ib exhibits a slightly lenient binding selectivity compared to that of meta‐II.