Structural alterations for proton translocation in the M state of wild-type bacteriorhodopsin

摘要: The transport of protons across membranes is an important process in cellular bioenergetics. light-driven proton pump bacteriorhodopsin the best-characterized protein providing this function. Photon energy absorbed by chromophore retinal, covalently bound to Lys 216 via a protonated Schiff base. light-induced all-trans 13-cis isomerization retinal results deprotonation base followed alterations protonatable groups within bacteriorhodopsin. changed force field induces changes, even tertiary structure1,2,3, which are necessary for pumping. recent report4 high-resolution X-ray crystal structure late M intermediate mutant bacteriorhopsin (with Asp 96→Asn) displays pathway highly disturbed mutation. To observe unperturbed pathway, we determined wild-type (2.25 A resolution). cytoplasmic side our M2 shows water net that allows transfer from donor group Asp 96 towards An enlarged cavity system above observed, facilitates de- and reprotonation fluctuating molecules last part cycle.