Rhodopsin mutants that bind but fail to activate transducin

Journal Article · Fri Oct 05 04:00:00 EDT 1990 · Science (Washington, D.C.); (USA)

DOI:https://doi.org/10.1126/science.2218504· OSTI ID:5923473

Franke, R R; Sakmar, T P; Khorana, H G ^[1]; Koenig, B; Hofmann, K P ^[2]

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1. Massachusetts Institute of Technology, Cambridge (USA)
2. Universitaet Freiburg (West Germany)

Rhodopsin is a member of a family of receptors that contain seven transmembrane helices and are coupled to G proteins. The nature of the interactions between rhodopsin mutants and the G protein, transducin (G{sub t}), was investigated by flash photolysis in order to monitor directly G{sub t} binding and dissociation. Three mutant opsins with alterations in their cytoplasmic loops bound 11-cis-retinal to yield pigments with native rhodopsin absorption spectra, but they failed to stimulate the guanosine triphosphatase activity of G{sub t}. The opsin mutations included reversal of a charged pair conserved in all G protein-coupled receptors at the cytoplasmic border to the third transmembrane helix (mutant CD1), replacement of 13 amino acids in the second cytoplasmic loop (mutant CD2), and deletion of 13 amino acids from the third cytoplasmic loop (mutant EF1). Whereas mutant CD1 failed to bind G{sub t}, mutants CD2 and EF1 showed normal G{sub t} binding but failed to release G{sub t} in the presence of guanosine triphosphate. Therefore, it appears that at least the second and third cytoplasmic loops of rhodopsin are required for activation of bound G{sub t}.

• OSTI ID: 5923473
• Journal Information: Science (Washington, D.C.); (USA), Journal Name: Science (Washington, D.C.); (USA) Vol. 250:4977; ISSN SCIEA; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTRA
BIOCHEMICAL REACTION KINETICS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CYTOPLASM
DECOMPOSITION
ENZYME ACTIVITY
ENZYMES
ESTERASES
HYDROLASES
KINETICS
MOLECULAR STRUCTURE
MUTANTS
ORGANIC COMPOUNDS
PHOSPHATASES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PIGMENTS
PROTEINS
REACTION KINETICS
RHODOPSIN
SPECTRA