Distinct roles of the second and third cytoplasmic loops of bovine rhodopsin in G protein activation.
J Biol Chem
; 275(44): 34272-9, 2000 Nov 03.
Article
in En
| MEDLINE
| ID: mdl-10930404
ABSTRACT
In contrast to the extensive studies of light-induced conformational changes in rhodopsin, the cytoplasmic architecture of rhodopsin related to the G protein activation and the selective recognition of G protein subtype is still unclear. Here, we prepared a set of bovine rhodopsin mutants whose cytoplasmic loops were replaced by those of other ligand-binding receptors, and we compared their ability for G protein activation in order to obtain a clue to the roles of the second and third cytoplasmic loops of rhodopsin. The mutants bearing the third loop of four other G(o)-coupled receptors belonging to the rhodopsin superfamily showed significant G(o) activation, indicating that the third loop of rhodopsin possibly has a putative site(s) related to the interaction of G protein and that it is simply exchangeable with those of other G(o)-coupled receptors. The mutants bearing the second loop of other receptors, however, had little ability for G protein activation, suggesting that the second loop of rhodopsin contains a specific region essential for rhodopsin to be a G protein-activating form. Systematic chimeric and point mutational studies indicate that three amino acids (Glu(134), Val(138), and Cys(140)) in the N-terminal region of the second loop of rhodopsin are crucial for efficient G protein activation. These results suggest that the second and third cytoplasmic loops of bovine rhodopsin have distinct roles in G protein activation and subtype specificity.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Rhodopsin
/
Cytoplasm
Limits:
Animals
Language:
En
Journal:
J Biol Chem
Year:
2000
Document type:
Article
Affiliation country: