Department of Biophysics, Medical College of Wisconsin, Milwaukee, USA.
J Biol Inorg Chem. 2010 Jun;15(5):749-58. doi: 10.1007/s00775-010-0643-0. Epub 2010 Mar 13.
The protein OmcA from the bacterium Shewanella oneidensis was purified to homogeneity, and characterized using UV-vis spectroelectrochemistry, EPR, and circular dichroism (far- and near-UV regions). EPR spectroscopy showed that many different c-type hemes are present in the protein: high-spin, low-spin, and highly anisotropic low-spin hemes were all detected. The protein was shown to bind tightly to artificial membranes (liposomes) composed of dioleoylphosphatidylglycerol and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (60:40 molar ratio), which mimic the natural environment. However, on the basis of the spectroscopic and electrochemical studies, binding to liposomes does not appear to significantly alter either the structure or the properties of OmcA. On the other hand, the electrochemical properties of OmcA are noticeably changed in the presence of the detergents used during the initial purification stages. In particular, the reduction potentials of two out of the ten OmcA hemes appear to shift in the presence of detergent, perhaps because these hemes are solvent-exposed.
从希瓦氏菌（Shewanella oneidensis）中纯化得到的蛋白质 OmcA，并通过紫外可见光谱电化学、电子顺磁共振（EPR）和圆二色性（远-近紫外区）对其进行了表征。EPR 光谱表明，该蛋白质中存在许多不同的 c 型血红素：检测到高自旋、低自旋和高度各向异性的低自旋血红素。该蛋白质被证明可以紧密结合由二油酰基磷脂酰甘油和 1-棕榈酰基-2-油酰基-sn-甘油-3-磷酸乙醇胺（摩尔比为 60:40）组成的人工膜（脂质体），这模拟了自然环境。然而，根据光谱和电化学研究，脂质体的结合似乎并没有显著改变 OmcA 的结构或性质。另一方面，在初始纯化阶段使用的去污剂的存在下，OmcA 的电化学性质明显发生变化。特别是，在去污剂存在的情况下，十个 OmcA 血红素中的两个的还原电位似乎发生了偏移，这可能是因为这些血红素暴露在溶剂中。
