3qbk | pdb_00003qbk

Bromide-bound form of pharaonis halorhodopsin

spinqualitylabelsall models 3qbk, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3qbk is a 3 chain structure with sequence from Natronomonas pharaonis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: 22B, BR, RET Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function BACH_NATPH Light-driven anion pump. Binding affinity for the anions is in the order, bromide > chloride > nitrate > azide > bromate and binding is pH dependent. Publication Abstract from PubMed Halorhodopsin from Natronomonas pharaonis (pHR) was previously crystallized into a monoclinic space group C2, and the structure of the chloride-bound purple form was determined. Here, we report the crystal structures of two chloride-free forms of pHR, that is, an O-like blue form and an M-like yellow form. When the C2 crystal was soaked in a chloride-free alkaline solution, the protein packing was largely altered and the yellow form containing all-trans retinal was generated. Upon neutralization, this yellow form was converted into the blue form. From structural comparison of the different forms of pHR, it was shown that the removal of a chloride ion from the primary binding site (site I), which is located between the retinal Schiff base and Thr126, is accompanied by such a deformation of helix C that the side chain of Thr126 moves toward helix G, leading to a significant shrinkage of site I. A large structural change is also induced in the chloride uptake pathway, where a flip motion of the side chain of Glu234 is accompanied by large movements of the surrounding aromatic residues. Irrespective of different charge distributions at the active site, there was no large difference in the structures of the yellow form and the blue form. It is shown that the yellow-to-purple transition is initiated by the entrance of one water and one HCl to the active site, where the proton and the chloride ion in HCl are transferred to the Schiff base and site I, respectively. Crystal structures of an O-like blue form and an anion-free yellow form of pharaonis halorhodopsin.,Kanada S, Takeguchi Y, Murakami M, Ihara K, Kouyama T J Mol Biol. 2011 Oct 14;413(1):162-76. Epub 2011 Aug 16. PMID:21871461 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Bacteriorhodopsin 3D structures Rhodopsin 3D structures

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