Vadyvaloo Viveka, Smirnova Irina N, Kasho Vladimir N, Kaback H Ronald
Department of Physiology and Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095-7327, USA.
J Mol Biol. 2006 May 12;358(4):1051-9. doi: 10.1016/j.jmb.2006.02.050. Epub 2006 Mar 9.
Building a three-dimensional model of the sucrose permease of Escherichia coli (CscB) with the X-ray crystal structure lactose permease (LacY) as template reveals a similar overall fold for CscB. Moreover, despite only 28% sequence identity and a marked difference in substrate specificity, the structural organization of the residues involved in sugar-binding and H(+) translocation is conserved in CscB. Functional analyses of mutants in the homologous key residues provide strong evidence that they play a similar critical role in the mechanisms of CscB and LacY.
以X射线晶体结构乳糖通透酶（LacY）为模板构建大肠杆菌蔗糖通透酶（CscB）的三维模型，结果显示CscB具有相似的整体折叠结构。此外，尽管CscB与LacY的序列同一性仅为28%，且底物特异性存在显著差异，但参与糖结合和H(+)转运的残基的结构组织在CscB中是保守的。对同源关键残基突变体的功能分析提供了有力证据，表明它们在CscB和LacY的机制中发挥相似的关键作用。
