Yoneyama H, Nakae T
Department of Molecular Life Science, Tokai University, School of Medicine, Isehara, Japan.
Microbiology (Reading). 1996 Aug;142 ( Pt 8):2137-44. doi: 10.1099/13500872-142-8-2137.
Protein C (OprC) of the outer membrane of Pseudomonas aeruginosa forms small channels, as assayed by the liposome swelling method. We report here that OprC functions as a channel-forming and copper-binding protein. OprC purified to homogeneity formed a channel in planar lipid bilayers with an ion conductance of about 200 pS in 1 M NaCl. Cloning and sequencing of the gene encoding OprC revealed that it specified a polypeptide comprising 723 and 668 amino acid residues for the precursor and mature polypeptides (M(r) 73,372), respectively. The amino acid sequence of OprC showed the highest degree of similarity with that of NosA of Pseudomonas stutzeri (65% sequence identity) which conveys Cu2+ to intracellular acceptor(s). OprC showed high copper-binding activity (Kd = 2.6 microM) in aqueous solution containing surfactant. The expression of OprC appeared to be repressed by exogenous Cu2+ and derepressed by anaerobiosis in the presence of nitrate. These results suggest that OprC might be involved in copper utilization.
通过脂质体膨胀法检测发现，铜绿假单胞菌外膜蛋白C（OprC）可形成小通道。我们在此报告，OprC作为一种通道形成和铜结合蛋白发挥作用。纯化至同质的OprC在平面脂质双分子层中形成通道，在1 M NaCl中离子电导约为200 pS。编码OprC的基因克隆和测序显示，其前体多肽和成熟多肽（M(r) 73,372）分别由723和668个氨基酸残基组成。OprC的氨基酸序列与施氏假单胞菌的NosA氨基酸序列相似度最高（序列同一性为65%），后者将Cu2+转运至细胞内受体。在含有表面活性剂的水溶液中，OprC表现出高铜结合活性（Kd = 2.6 microM）。在硝酸盐存在的情况下，OprC的表达似乎受到外源Cu2+的抑制，并在厌氧条件下解除抑制。这些结果表明，OprC可能参与铜的利用。
