Armstrong S K, Parr T R, Parker C D, Hancock R E
J Bacteriol. 1986 Apr;166(1):212-6. doi: 10.1128/jb.166.1.212-216.1986.
The major outer membrane protein of molecular weight 40,000 (the 40K protein) of a virulent isolate of Bordetella pertussis was purified to apparent homogeneity. The purified protein formed an oligomer band (of apparent molecular weight 90,000) on sodium dodecyl sulfate-polyacrylamide gels after solubilization at low temperatures. The porin function of this protein was characterized by the black lipid bilayer method. The 40K protein formed channels smaller than all other constitutive major outer membrane porins studied to date. The average single-channel conductance in 1 M KCl was 0.56 nS. This was less than a third of the conductance previously observed for Escherichia coli porins. Zero-current potential measurements made of the porin to determine its ion selectivity revealed the porin to be more than 100-fold selective for anions over cations. The single-channel conductance was measured as a function of salt concentration. The data could be fitted to a Lineweaver-Burk plot suggesting an anion binding site with a Kd of 1.17 M Cl- and a maximum possible conductance through the channel of 1.28 nS.
百日咳博德特氏菌强毒株分子量为40,000的主要外膜蛋白（40K蛋白）被纯化至表观均一。纯化后的蛋白在低温溶解后，于十二烷基硫酸钠-聚丙烯酰胺凝胶上形成一条寡聚体带（表观分子量90,000）。该蛋白的孔蛋白功能通过黑色脂质双分子层法进行表征。40K蛋白形成的通道比迄今研究的所有其他组成性主要外膜孔蛋白都小。在1 M KCl中，平均单通道电导为0.56 nS。这不到先前观察到的大肠杆菌孔蛋白电导的三分之一。通过对孔蛋白进行零电流电位测量以确定其离子选择性，结果显示该孔蛋白对阴离子的选择性比对阳离子高100倍以上。测量了单通道电导随盐浓度的变化。数据可拟合到Lineweaver-Burk图，表明存在一个阴离子结合位点，其Kd为1.17 M Cl⁻，通道的最大可能电导为1.28 nS。
