title: The site of attachment of retinal in bacteriorhodopsin. The epsilon-amino group in Lys-41 is not required for proton translocation.
abstract: Chymotryptic fragments C-1 (amino acids 72-248) and C-2 (amino acids 1-71) of bacteriorhodopsin have been shown previously to reassociate so as to regenerate the native bacteriorhodopsin chromophore in lipid/detergent mixtures and to form functional proton-translocating vesicles. The fragment C-2 has now been selectively methylated with formaldehyde and sodium cyanoborohydride to give the epsilon-dimethylamino derivatives of Lys-30, 40, and 41 in 96-99% average yield. The methylated and unmethylated C-2 fragments were identical in their ability to reassociate with fragment C-1 and retinal to regenerate the bacteriorhodopsin chromophore and to form functional proton-translocating vesicles. In contrast, dimethylation of the lysine residues of the C-1 fragment gave a derivative which did not form an active complex with unmethylated C-2. We conclude that the epsilon-amino group in Lys-41 is not required for Schiff's base formation with retinal at any step in the light-driven proton-translocation cycle.
mesh_terms: D001436:Bacteriorhodopsins / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D007700:Kinetics; D008239:Lysine; D008745:Methylation; D010446:Peptide Fragments / Q000378:metabolism; D011522:Protons; D012172:Retinaldehyde / Q000378:metabolism*; D013053:Spectrophotometry; D014801:Vitamin A / Q000031:analogs & derivatives*
chemical_list: D010446:Peptide Fragments; D011522:Protons; D014801:Vitamin A; D002338:Carotenoids; D001436:Bacteriorhodopsins; D002918:Chymotrypsin; D008239:Lysine; D012172:Retinaldehyde