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Asymmetric states of vitamin B₁₂ transporter BtuCD are not discriminated by its cognate substrate binding protein BtuF.

FEBS Lett.2012 Apr 05;586(7):972-6. Epub 2012 Mar 08
Vladimir M Korkhov 1 , Samantha A Mireku , Rikki N Hvorup , Kaspar P Locher
Vladimir M Korkhov 1 , Samantha A Mireku , Rikki N Hvorup , Kaspar P Locher

[No authors listed]

Author information
  • 1 Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland.

摘要


BtuCD is an ABC transporter catalyzing the uptake of vitamin B₁₂ across the Escherichia coli inner membrane. A previously reported X-ray structure of BtuCD in complex with the periplasmic vitamin B₁₂-binding protein BtuF revealed asymmetry of the transmembrane BtuC subunits. The functional relevance of this asymmetry has remained uncertain. Here we report the X-ray structure of a catalytically impaired BtuCD mutant in complex with BtuF, where the BtuC subunits adopt a distinct asymmetric conformation. The structure suggests that BtuF does not discriminate between, or impose, asymmetric conformations of BtuCD. It also explains the conformational disorder observed in BtuCDF crystals.