The crystal structure of putative precorrin isomerase CbiC in cobalamin biosynthesis

National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, PR China.
Journal of Structural Biology (Impact Factor: 3.23). 04/2006; 153(3):307-11. DOI: 10.1016/j.jsb.2005.11.011
Source: PubMed


The leptospira cbiC encodes the enzyme catalyzing the methyl rearrangement reaction of the cobalamin biosynthesis pathway. The protein has been cloned and overexpressed as a His-tagged recombinant protein in Escherichia coli. The crystal structures have been solved in two crystal forms (P4(2)2(1)2 and P3(1)21) diffracting to 3.0 and 2.3A resolution, respectively. The structures are similar to the precorrin-8x methyl mutase (CobH), an enzyme of the aerobic pathway to vitamin B12.

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    • "Experimental evidence for the functions of CbiB, -H, -K, and –L, and for those of CbiA, -D, -F, -G, and –T, among the 13 catalytic Cbi proteins, was also recently reported [15-17]. However, only the crystal structures of CbiC [18], CbiF [19], CbiK [20], CbiL [21] and CbiT [22] have been solved. "
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    ABSTRACT: Background In the anaerobic pathway of cobalamin (vitamin B12) synthesis, the CbiT enzyme plays two roles, as a cobalt-precorrin-7 C15-methyltransferase and a C12-decarboxylase, to produce the intermediate, cobalt-precorrin 8. Results The primary structure of the hypothetical protein MJ0391, from Methanocaldococcus jannaschii, suggested that MJ0391 is a putative CbiT. Here, we report the crystal structure of MJ0391, solved by the MAD procedure and refined to final R-factor and R-free values of 19.8 & 27.3%, respectively, at 2.3 Å resolution. The asymmetric unit contains two NCS molecules, and the intact tetramer generated by crystallographic symmetry may be functionally important. The overall tertiary structure and the tetrameric arrangements are highly homologous to those found in MT0146/CbiT from Methanobacterium thermoautotrophicum. Conclusions The conservation of functional residues in the binding site for the co-factor, AdoMet, and in the putative precorrin-7 binding pocket suggested that MJ0391 may also possess CbiT activity. The putative function of MJ0391 is discussed, based on structural homology.
    Full-text · Article · May 2013 · BMC Structural Biology