Structure-function studies on bacteriorhodopsin. V. Effects of amino acid substitutions in the putative helix F.

摘要: Abstract To test structural and mechanistic proposals about bacteriorhodopsin, a series of analogues with single amino acid substitutions has been studied. Mutants in the proposed helix F bacteriorhodopsin were chosen for investigation because probable interaction this part protein retinal chromophore. Seven mutants gene constructed by site-directed mutagenesis, products expressed Escherichia coli. The resulting mutant proteins purified assayed their ability to interact phospholipid/detergent micelles form bacteriorhodopsin-like Four mutants, Ser-183----Ala, Tyr-185----Phe, Ser-193----Ala, Glu-194----Gln, bound give pigments absorption maxima approximately same as wild type. Three opsins chromophores that blue-shifted relative Two Trp----Phe at positions 182 189 gave 480 524 nm, respectively, Pro-186----Leu pigment an maximum 470 nm. However, none eliminated pump protons response illumination.