3m8b

Crystal structure of spin-labeled BtuB V10R1 in the apo state

spinqualitylabelsall models 3m8b, resolution 2.44Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3m8b is a 1 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: C8E, MG, MTN Related: 3m8d Gene: btuB, bfe, cer, dcrC, b3966, JW3938 (Escherichia coli) Resources: FirstGlance, OCA, RCSB, PDBsum Function [BTUB_ECOLI] Involved in the active translocation of vitamin B12 (cyanocobalamin) across the outer membrane to the periplasmic space. It derives its energy for transport by interacting with the trans-periplasmic membrane protein TonB. Is also a receptor for bacteriophages BF23 and C1, and for A and E colicins.[HAMAP-Rule:MF_01531] 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 Successful macromolecular crystallography requires solution conditions that may alter the conformational sampling of a macromolecule. Here, site-directed spin labeling is used to examine a conformational equilibrium within BtuB, the Escherichia coli outer membrane transporter for vitamin B(12). Electron paramagnetic resonance (EPR) spectra from a spin label placed within the N-terminal energy coupling motif (Ton box) of BtuB indicate that this segment is in equilibrium between folded and unfolded forms. In bilayers, substrate binding shifts this equilibrium toward the unfolded form; however, EPR spectra from this same spin-labeled mutant indicate that this unfolding transition is blocked in protein crystals. Moreover, crystal structures of this spin-labeled mutant are consistent with the EPR result. When the free energy difference between substates is estimated from the EPR spectra, the crystal environment is found to alter this energy by 3 kcal/mol when compared to the bilayer state. Approximately half of this energy change is due to solutes or osmolytes in the crystallization buffer, and the remainder is contributed by the crystal lattice. These data provide a quantitative measure of how a conformational equilibrium in BtuB is modified in the crystal environment, and suggest that more-compact, less-hydrated substates will be favored in protein crystals. Conformational exchange in a membrane transport protein is altered in protein crystals.,Freed DM, Horanyi PS, Wiener MC, Cafiso DS Biophys J. 2010 Sep 8;99(5):1604-10. PMID:20816073 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also BtuB

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