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.

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