1qko
From Proteopedia
HIGH RESOLUTION X-RAY STRUCTURE OF AN EARLY INTERMEDIATE IN THE BACTERIORHODOPSIN PHOTOCYCLE
Overview
Bacteriorhodopsin is the simplest known photon-driven proton pump and as such provides a model for the study of a basic function in bioenergetics. Its seven transmembrane helices encompass a proton translocation pathway containing the chromophore, a retinal molecule covalently bound to lysine 216 through a protonated Schiff base, and a series of proton donors and acceptors. Photoisomerization of the all-trans retinal to the 13-cis configuration initiates the vectorial translocation of a proton from the Schiff base, the primary proton donor, to the extracellular side, followed by reprotonation of the Schiff base from the cytoplasm. Here we describe the high-resolution X-ray structure of an early intermediate in the photocycle of bacteriorhodopsin, which is formed directly after photoexcitation. A key water molecule is dislocated, allowing the primary proton acceptor, Asp 85, to move. Movement of the main-chain Lys 216 locally disrupts the hydrogen-bonding network of helix G, facilitating structural changes later in the photocycle.
About this Structure
1QKO is a Single protein structure of sequence from Halobacterium salinarum. Full crystallographic information is available from OCA.
Reference
High-resolution X-ray structure of an early intermediate in the bacteriorhodopsin photocycle., Edman K, Nollert P, Royant A, Belrhali H, Pebay-Peyroula E, Hajdu J, Neutze R, Landau EM, Nature. 1999 Oct 21;401(6755):822-6. PMID:10548112 Page seeded by OCA on Sat May 3 06:23:21 2008
