8c7p

Tagless BtuM in complex with cyanocobalamin

spinqualitylabelsall models 8c7p, resolution 3.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8c7p is a 1 chain structure with sequence from Thiobacillus denitrificans ATCC 25259. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q3SFD8_THIDA Publication Abstract from PubMed BtuM is a bacterial cobalamin transporter that binds the transported substrate in the base-off state, with a cysteine residue providing the alpha-axial coordination of the central cobalt ion via a sulfur-cobalt bond. Binding leads to decyanation of cobalamin variants with a cyano group as the beta-axial ligand. Here, we report the crystal structures of untagged BtuM bound to two variants of cobalamin, hydroxycobalamin and cyanocobalamin, and unveil the native residue responsible for the beta-axial coordination, His28. This coordination had previously been obscured by non-native histidines of His-tagged BtuM. A model in which BtuM initially binds cobinamide reversibly with low affinity (K(D) = 4.0 muM), followed by the formation of a covalent bond (rate constant of 0.163 s(-1)), fits the kinetics data of substrate binding and decyanation of the cobalamin precursor cobinamide by BtuM. The covalent binding mode suggests a mechanism not used by any other transport protein. Cobalamin decyanation by the membrane transporter BtuM.,Martinez Felices JM, Barreto YB, Thangaratnarajah C, Whittaker JJ, Alencar AM, Guskov A, Slotboom DJ Structure. 2024 Aug 8;32(8):1165-1173.e3. doi: 10.1016/j.str.2024.04.014. Epub , 2024 May 10. PMID:38733996 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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