De Pinto V, Benz R, Caggese C, Palmieri F
Dipartimento Farmaco-Biologico, Università di Bari, Italy.
Biochim Biophys Acta. 1989 Dec 11;987(1):1-7. doi: 10.1016/0005-2736(89)90447-1.
Mitochondrial porin was isolated from the fruit fly Drosophila melanogaster at different developmental stages, starting from whole mitochondria. The porin from adults' mitochondria was fully characterized. The protein had a molecular mass of 31 kDa as judged from sodium dodecylsulfate electrophoretograms. It was very resistive against digestion with V8 proteinase of Staphylococcus aureus and a larger number of fragments were only obtained after digestion with papain. Drosophila porin showed little interaction with antibodies raised against mitochondrial porins from mammalia and Neurospora crassa, but a strong reactivity with antibodies raised against yeast porin. Reconstitution experiments with planar lipid bilayer membranes showed that the protein was able to form ion-permeable pores with a single-channel conductance of 0.41 nS in 0.1 M KCl. At low transmembrane voltages Drosophila porin had the properties of a general diffusion pore with an estimated effective diameter of about 1.7 nm and a small selectivity for anions over cations. Voltages larger than 20 to 30 mV resulted in a closure of the pore. The closed states of the pore were found to be cation-selective. The addition of a synthetic polyanion to the aqueous phase on one side of the membrane resulted in an asymmetric shift of the voltage dependence and the pore became already closed at very small voltages negative at the cis-side (the side of the addition of the polyanion).
线粒体孔蛋白是从果蝇（Drosophila melanogaster）不同发育阶段的全线粒体中分离出来的。已对成年果蝇线粒体中的孔蛋白进行了全面表征。根据十二烷基硫酸钠电泳图谱判断，该蛋白的分子量为31 kDa。它对金黄色葡萄球菌V8蛋白酶的消化具有很强的抗性，只有在用木瓜蛋白酶消化后才获得大量片段。果蝇孔蛋白与针对哺乳动物和粗糙脉孢菌线粒体孔蛋白产生的抗体几乎没有相互作用，但与针对酵母孔蛋白产生的抗体具有很强的反应性。用平面脂质双分子层膜进行的重组实验表明，该蛋白能够形成离子通透孔，在0.1 M KCl中的单通道电导为0.41 nS。在低跨膜电压下，果蝇孔蛋白具有一般扩散孔的特性，估计有效直径约为1.7 nm，对阴离子的选择性略高于阳离子。大于20至30 mV的电压会导致孔关闭。发现孔的关闭状态具有阳离子选择性。在膜一侧的水相中添加合成聚阴离子会导致电压依赖性的不对称偏移，并且在顺侧（添加聚阴离子的一侧）非常小的负电压下孔就已经关闭。
