Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland.
FEBS Lett. 2012 Apr 5;586(7):972-6. doi: 10.1016/j.febslet.2012.02.042. Epub 2012 Mar 8.
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.
BtuCD 是一种 ABC 转运蛋白，可催化大肠杆菌内膜对维生素 B₁₂的摄取。先前报道的 BtuCD 与周质维生素 B₁₂结合蛋白 BtuF 形成复合物的 X 射线结构显示跨膜 BtuC 亚基的不对称性。这种不对称性的功能相关性一直不确定。在这里，我们报告了与 BtuF 形成复合物的催化缺陷 BtuCD 突变体的 X 射线结构，其中 BtuC 亚基采用独特的不对称构象。该结构表明 BtuF 不会区分或强加 BtuCD 的不对称构象。它还解释了在 BtuCDF 晶体中观察到的构象无序。
