1m0k | pdb_00001m0k

BACTERIORHODOPSIN K INTERMEDIATE AT 1.43 A RESOLUTION

spinqualitylabelsall models 1m0k, resolution 1.43Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1m0k is a 1 chain structure with sequence from "bacillus_halobius_ruber"_klebahn_1919 "bacillus halobius ruber" klebahn 1919. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: LI1, RET, SQU Related: 1m0l, 1m0m Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [BACR_HALSA] Light-driven proton pump. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed The K state, an early intermediate of the bacteriorhodopsin photocycle, contains the excess free energy used for light-driven proton transport. The energy gain must reside in or near the photoisomerized retinal, but in what form has long been an open question. We produced the K intermediate in bacteriorhodopsin crystals in a photostationary state at 100K, with 40% yield, and determined its X-ray diffraction structure to 1.43 A resolution. In independent refinements of data from four crystals, the changes are confined mainly to the photoisomerized retinal. The retinal is 13-cis,15-anti, as known from vibrational spectroscopy. The C13=C14 bond is rotated nearly fully to cis from the initial trans configuration, but the C14-C15 and C15=NZ bonds are partially counter-rotated. This strained geometry keeps the direction of the Schiff base N-H bond vector roughly in the extracellular direction, but the angle of its hydrogen bond with water 402, that connects it to the anionic Asp85 and Asp212, is not optimal. Weakening of this hydrogen bond may account for many of the reported features of the infrared spectrum of K, and for its photoelectric signal, as well as the deprotonation of the Schiff base later in the cycle. Importantly, although 13-cis, the retinal does not assume the expected bent shape of this configuration. Comparison of the calculated energy of the increased angle of C12-C13=C14, that allows this distortion, with the earlier reported calorimetric measurement of the enthalpy gain of the K state indicates that a significant part of the excess energy is conserved in the bond strain at C13. Crystallographic structure of the K intermediate of bacteriorhodopsin: conservation of free energy after photoisomerization of the retinal.,Schobert B, Cupp-Vickery J, Hornak V, Smith S, Lanyi J J Mol Biol. 2002 Aug 23;321(4):715-26. PMID:12206785 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Bacteriorhodopsin 3D structures

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