X-ray structural characterization of imidazolylcobalamin and histidinylcobalamin: cobalamin models for aquacobalamin bound to the B12 transporter protein transcobalamin

Inorg Chem. 2007 Apr 30;46(9):3613-8. doi: 10.1021/ic070022n. Epub 2007 Apr 4.

Abstract

The X-ray structures of imidazolylcobalamin (ImCbl) and histidinylcobalamin (HisCbl) are reported. These structures are of interest given that the recent structures of human and bovine transcobalamin prepared in their holo forms from aquacobalamin show a histidine residue of the metalloprotein bound at the beta-axial site of the cobalamin (Wuerges, J. et al. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 4386-4391). The beta-axial Co-N bond distances for ImCbl and HisCbl are 1.94(1) and 1.951(7) A, respectively. The alpha-axial Co-N bond distances to the 5,6-dimethylbenzimidazole are 2.01(1) and 1.979(8) A for ImCbl and HisCbl, respectively, and are typical for cobalamins with weak sigma-donor ligands at the beta-axial site. The corrin fold angles of 11.8(3) degrees (ImCbl) and 12.0(3) degrees (HisCbl) are smaller than those typically observed for cobalamins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Histidine / chemistry*
  • Imidazoles / chemistry*
  • Ligands
  • Models, Biological*
  • Models, Molecular
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Transcobalamins / chemistry*
  • Transcobalamins / metabolism*
  • Vitamin B 12 / analogs & derivatives
  • Vitamin B 12 / chemical synthesis
  • Vitamin B 12 / chemistry*
  • Vitamin B 12 / metabolism*

Substances

  • Imidazoles
  • Ligands
  • Transcobalamins
  • Histidine
  • imidazole
  • Vitamin B 12