Journal of Structural and Functional Genomics

, Volume 7, Issue 1, pp 37–50

Crystal Structure of the Vitamin B12 Biosynthetic Cobaltochelatase, CbiXS, from Archaeoglobus Fulgidus

Authors

    • Group in Protein Structure and Function, Department of BiochemistryUniversity of Alberta
  • Linda X. Xu
    • Ontario Centre for Structural ProteomicsC.H. Best Institute, University of Toronto
  • Maia M. Cherney
    • Group in Protein Structure and Function, Department of BiochemistryUniversity of Alberta
  • Evelyne Raux-Deery
    • Department of BiosciencesUniversity of Kent
  • Amanda A. Bindley
    • Department of BiosciencesUniversity of Kent
  • Alexei Savchenko
    • Ontario Centre for Structural ProteomicsC.H. Best Institute, University of Toronto
  • John R. Walker
    • Ontario Centre for Structural ProteomicsC.H. Best Institute, University of Toronto
  • Marianne E. Cuff
    • Structural Biology Center & Midwest Center for Structural GenomicsBiosciences Division Argonne National Laboratory
  • Martin J. Warren
    • Department of BiosciencesUniversity of Kent
  • Michael N. G. James
    • Group in Protein Structure and Function, Department of BiochemistryUniversity of Alberta
    • Alberta Synchrotron InstituteUniversity of Alberta
ORIGINAL PAPER

DOI: 10.1007/s10969-006-9008-x

Cite this article as:
Yin, J., Xu, L.X., Cherney, M.M. et al. J Struct Funct Genomics (2006) 7: 37. doi:10.1007/s10969-006-9008-x

Abstract

The Archaeoglobus fulgidus gene af0721 encodes CbiXS, a small cobaltochelatase associated with the anaerobic biosynthesis of vitamin B12 (cobalamin). The protein was shown to have activity both in vivo and in vitro, catalyzing the insertion of Co2+ into sirohydrochlorin. The structure of CbiXS was determined in two different crystal forms and was shown to consist of a central mixed β-sheet flanked by four α-helices, one of which originates in the C-terminus of a neighboring molecule. CbiXS is about half the size of other Class II tetrapyrrole chelatases. The overall topography of CbiXS exhibits substantial resemblance to both the N- and C-terminal regions of several members of the Class II metal chelatases involved in tetrapyrrole biosynthesis. Two histidines (His10 and His74), are in similar positions as the catalytic histidine residues in the anaerobic cobaltochelatase CbiK (His145 and His207). In light of the hypothesis that suggests the larger chelatases evolved via gene duplication and fusion from a CbiXS-like enzyme, the structure of AF0721 may represent that of an “ancestral” precursor of class II metal chelatases.

Keywords

Cobalamin (vitamin B12) biosynthesisTetrapyrroleCbiKCbiXCobaltochelataseProtein structure evolution

Supplementary material

Copyright information

© Springer Science+Business Media B.V. 2006