Martinez M C, Lazdunski C, Pattus F
Centre de Biochimie et de Biologie Moléculaire du CNRS, Marseille, France.
EMBO J. 1983;2(9):1501-7. doi: 10.1002/j.1460-2075.1983.tb01614.x.
Partial proteolytic digestion of colicin A with bromelain allowed the isolation of a 20-kd fragment. This fragment has been purified to homogeneity and its molecular properties have been studied. The sequence of the 54 N-terminal amino acid residues has been determined by automated Edman degradation. This sequence is identical to that of the predicted amino acid sequence of the 20-kd C-terminal part of the colicin A polypeptide deduced from the nucleotide sequence of the caa gene. This polypeptide can produce channels in phospholipid planar bilayers of the same size as those formed by colicin A. However, the voltage-dependence for opening and closing was drastically altered in the peptide fragment channels. The latter, in contrast to colicin A channels, remained open over a wide range of voltage. Large negative potentials were required to close the peptide fragment channels although opening took place in the same voltage range as for colicin A ionic pores.
用菠萝蛋白酶对大肠菌素A进行部分蛋白酶解可分离出一个20 kDa的片段。该片段已纯化至同质，并对其分子特性进行了研究。通过自动埃德曼降解法确定了54个N端氨基酸残基的序列。该序列与从caa基因核苷酸序列推导的大肠菌素A多肽20 kDa C端部分的预测氨基酸序列相同。该多肽可在磷脂平面双分子层中形成与大肠菌素A形成的通道大小相同的通道。然而，肽片段通道的开闭电压依赖性发生了显著改变。与大肠菌素A通道相比，后者在很宽的电压范围内保持开放。虽然肽片段通道的开放电压范围与大肠菌素A离子孔相同，但需要很大的负电位才能关闭。
