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 2.3 angstrom resolution, respectively. The structures are similar to the precorrin-8x methyl mutase (CobH), an enzyme of the aerobic pathway to vitamin B12. (C) 2005 Elsevier Inc. All rights reserved.