Bay Denice C, Turner Raymond J
Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
Biochim Biophys Acta. 2011 Sep;1808(9):2233-44. doi: 10.1016/j.bbamem.2011.05.005. Epub 2011 May 12.
Small multidrug resistance (SMR) protein family member, SugE, is an integral inner membrane protein that confers host resistance to antiseptic quaternary cation compounds (QCC). SugE studies generally focus on its resistance to limited substrates in comparison to SMR protein EmrE. This study examines the conformational characteristics of SugE protein in two detergents, sodium dodecyl sulphate (SDS) and dodecyl maltoside (DDM), commonly used to study SMR proteins. The influence of cetylpyridinium (CTP) and cetrimide (CET) using SugE aromatic residues (4W, 2Y, 1F) as intrinsic spectroscopic probes was also determined. Organically extracted detergent solubilized Escherichia coli SugE protein was examined by SDS-Tricine PAGE and various spectroscopic techniques. SDS-Tricine PAGE analysis of SugE in either detergent demonstrates the protein predominates as a monomer but also dimerizes in SDS. Far-UV region circular dichroism (CD) analysis determined that the overall α-helix content SugE in SDS and DDM was almost identical and unaltered by QCC. Near-UV region CD, fluorescence, and second-derivative ultraviolet absorption (SDUV) indicated that only DDM-SugE promoted hydrophobic environments for its Trp and Tyr residues that were perturbed by QCC addition. This study identified that only the tertiary structure of SugE protein in DDM is altered by QCC.
小多药耐药性（SMR）蛋白家族成员SugE是一种整合内膜蛋白，可赋予宿主对防腐季铵阳离子化合物（QCC）的抗性。与SMR蛋白EmrE相比，SugE的研究通常集中在其对有限底物的抗性上。本研究考察了常用于研究SMR蛋白的两种去污剂——十二烷基硫酸钠（SDS）和十二烷基麦芽糖苷（DDM）中SugE蛋白的构象特征。还确定了使用SugE芳香族残基（4个色氨酸、2个酪氨酸、1个苯丙氨酸）作为内在光谱探针时十六烷基吡啶（CTP）和西曲溴铵（CET）的影响。通过SDS-三羟甲基氨基甲烷聚丙烯酰胺凝胶电泳（SDS-Tricine PAGE）和各种光谱技术对有机萃取的去污剂溶解的大肠杆菌SugE蛋白进行了检测。对SugE在任一种去污剂中的SDS-Tricine PAGE分析表明，该蛋白主要以单体形式存在，但在SDS中也会二聚化。远紫外区域圆二色性（CD）分析确定，SugE在SDS和DDM中的整体α-螺旋含量几乎相同，且不受QCC影响。近紫外区域CD、荧光和二阶导数紫外吸收（SDUV）表明，只有DDM-SugE为其色氨酸和酪氨酸残基营造了疏水环境，添加QCC会对这种环境产生干扰。本研究确定，只有DDM中SugE蛋白的三级结构会因QCC而改变。
