Structure-function studies on bacteriorhodopsin. VIII. Substitutions of the membrane-embedded prolines 50, 91, and 186: The effects are determined by the substituting amino acids

Journal Article · Fri Aug 25 04:00:00 EDT 1989 · Journal of Biological Chemistry; (USA)

OSTI ID:5673834

Mogi, T; Stern, L J; Chao, B H; Khorana, H G ^[1]

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1. Massachusetts Institute of Technology, Cambridge (USA)

To study their role in the structure and function of bacteriorhodopsin, three prolines, presumed to be in the membrane-embedded alpha-helices, have been individually replaced as follows: Pro-50 and Pro-91 each by Gly and Ala and Pro-186 by Ala, Gly, and Val. The mutants of Pro-50 and Pro-91 all showed normal chromophore and proton pumping. However, the rates of regeneration of the chromophore in Pro-50----Ala, Pro-91----Ala and ----Gly with all-trans-retinal were about 30-fold slower than that in the wild-type, whereas the chromophore regeneration rate in Pro-50----Gly was 10-fold faster than in the wild-type. While, Pro-186----Ala regenerated the wild-type chromophore, the mutants Pro-186----Val and Pro-186----Gly showed large blue shifts (about 80 nm) in the chromophore regenerated with all-trans-retinal and showed no apparent dark-light adaptation. Pro-186----Gly first regenerated the wild-type chromophore with 13-cis-retinal which was thermally unstable and rapidly converted to the blue-shifted chromophore obtained with all-trans-retinal. High salt concentration restored the wild-type purple chromophore in the Pro-186----Gly mutant. Thus, in this mutant, the protein interconverts between two conformational states. Pro-186----Ala and Pro-186----Gly showed about 65%, whereas Pro-186----Val showed 10-20% of the normal proton pumping.

• OSTI ID: 5673834
• Journal Information: Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 264:24; ISSN JBCHA; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ALANINES
ALKALI METAL COMPOUNDS
AMINES
AMINO ACID SEQUENCE
AMINO ACIDS
AZOLES
BACTERIA
BARYONS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
CHLORIDES
CHLORINE COMPOUNDS
ELEMENTARY PARTICLES
FERMIONS
GLYCINE
HADRONS
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MEMBRANE PROTEINS
MEMBRANES
MICROORGANISMS
MOLECULAR STRUCTURE
MUTATIONS
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PROLINE
PROTEIN STRUCTURE
PROTEINS
PROTONS
PYRROLES
PYRROLIDINES
RHODOPSIN
SODIUM CHLORIDES
SODIUM COMPOUNDS
STRUCTURE-ACTIVITY RELATIONSHIPS
VALINE