Function

BtuB or vitamin B12 receptor or outer membrane cobalamin transporter is an outer membrane receptor found in a variety of bacteria, such as E. coli. BtuB transports vitamin B12 across the membrane of gram-negative bacteria. The transport is achieved with high affinity by the collaboration of BtuB and the periplasmic protein TonB. [1] As an essential receptor for the cell that is constitutively expressed, it is an ideal target to be parasitized, a feature exploited by a variety of proteins such as Colicins.

Structural highlights

BtuB depends on the presence of Ca+2 ions for high affinity . The .[2]

3D structure of BtuB

BtuB 3D structures


E. coli BtuB complex with cobalamin (a vitamin B12 derivative), lipid, methanesulfonothioate derivative and Ca+2 ions (green) (PDB code 3m8d)

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ReferencesReferences

  1. Chimento DP, Kadner RJ, Wiener MC. The Escherichia coli outer membrane cobalamin transporter BtuB: structural analysis of calcium and substrate binding, and identification of orthologous transporters by sequence/structure conservation. J Mol Biol. 2003 Oct 3;332(5):999-1014. PMID:14499604 doi:http://dx.doi.org/10.1016/S0022283603009975
  2. Freed DM, Horanyi PS, Wiener MC, Cafiso DS. Conformational exchange in a membrane transport protein is altered in protein crystals. Biophys J. 2010 Sep 8;99(5):1604-10. PMID:20816073 doi:10.1016/j.bpj.2010.06.026

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