5M34

Structure of cobinamide-bound BtuF mutant W66Y, the periplasmic vitamin B12 binding protein in E.coli

Summary for 5M34

• Entry DOI: 10.2210/pdb5m34/pdb
• Related: 1N2Z 1N4A 1N4D 5M29 5M2Q
• Descriptor: Vitamin B12-binding protein, COB(II)INAMIDE, CYANIDE ION, ... (5 entities in total)
• Functional Keywords: btuf, cobinamide, periplasmic binding protein, abc transporter, transport protein
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 65220.19

Authors

Mireku, S.A.,Ruetz, M.,Zhou, T.,Korkhov, V.M.,Kraeutler, B.,Locher, K.P. (deposition date: 2016-10-14, release date: 2017-03-01, Last modification date: 2024-10-16)

Primary citation

Mireku, S.A.,Ruetz, M.,Zhou, T.,Korkhov, V.M.,Krautler, B.,Locher, K.P.
Conformational Change of a Tryptophan Residue in BtuF Facilitates Binding and Transport of Cobinamide by the Vitamin B12 Transporter BtuCD-F.
Sci Rep, 7:41575-41575, 2017

PubMed Abstract: BtuCD-F is an ABC transporter that mediates cobalamin uptake into Escherichia coli. Early in vivo data suggested that BtuCD-F might also be involved in the uptake of cobinamide, a cobalamin precursor. However, neither was it demonstrated that BtuCD-F indeed transports cobinamide, nor was the structural basis of its recognition known. We synthesized radiolabeled cyano-cobinamide and demonstrated BtuCD-catalyzed in vitro transport, which was ATP- and BtuF-dependent. The crystal structure of cobinamide-bound BtuF revealed a conformational change of a tryptophan residue (W66) in the substrate binding cleft compared to the structure of cobalamin-bound BtuF. High-affinity binding of cobinamide was dependent on W66, because mutation to most other amino acids substantially reduced binding. The structures of three BtuF W66 mutants revealed that tight packing against bound cobinamide was only provided by tryptophan and phenylalanine, in line with the observed binding affinities. In vitro transport rates of cobinamide and cobalamin were not influenced by the substitutions of BtuF W66 under the experimental conditions, indicating that W66 has no critical role in the transport reaction. Our data present the molecular basis of the cobinamide versus cobalamin specificity of BtuCD-F and provide tools for in vitro cobinamide transport and binding assays.

PubMed: 28128319
DOI: 10.1038/srep41575

Experimental method

X-RAY DIFFRACTION (1.6 Å)