1iw6
From Proteopedia
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Crystal Structure of the Ground State of Bacteriorhodopsin
Overview
Bacteriorhodopsin, the sole membrane protein of the purple membrane of, Halobacterium salinarum, functions as a light-driven proton pump. A 3-D, crystal of bacteriorhodopsin, which was prepared by the membrane fusion, method, was used to investigate structural changes in the primary, photoreaction. It was observed that when a frozen crystal was exposed to a, low flux of X-ray radiation (5 x 10(14)photons mm(-2)), nearly half of the, protein was converted into an orange species, exhibiting absorption peaks, at 450 nm, 478 nm and 510 nm. The remainder retained the normal, photochemical activity until Asp85 in the active site was decarboxlyated, by a higher flux of X-ray radiation (10(16)photons mm(-2)). The procedure, of diffraction measurement was improved so as to minimize the effects of, the radiation damage and determine the true structural change associated, with the primary photoreaction. Our structural model of the K intermediate, indicates that the Schiff base linkage and the adjacent bonds in the, polyene chain of retinal are largely twisted so that the Schiff base, nitrogen atom still interacts with a water molecule located near Asp85., With respect to the other part of the protein, no appreciable displacement, is induced in the primary photoreaction.
About this Structure
1IW6 is a Single protein structure of sequence from Halobacterium salinarum with RET, L3P and L2P as ligands. Full crystallographic information is available from OCA.
Reference
Specific damage induced by X-ray radiation and structural changes in the primary photoreaction of bacteriorhodopsin., Matsui Y, Sakai K, Murakami M, Shiro Y, Adachi S, Okumura H, Kouyama T, J Mol Biol. 2002 Nov 29;324(3):469-81. PMID:12445782
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