Molecular cloning and sequencing of cDNA for yeast porin, an outer mitochondrial membrane protein: a search for targeting signal in the primary structure.
Molecular cloning and sequencing of cDNA for yeast porin, an outer mitochondrial membrane protein: a search for targeting signal in the primary structure.
复制标题
酵母孔蛋白（一种线粒体外膜蛋白）的 cDNA 分子克隆和测序：寻找一级结构中的靶向信号。
作者：
K. Mihara;R. Sato
我们克隆了酿酒酵母线粒体膜主要外膜蛋白--酵母孔蛋白的全长cDNA，并测定了其核苷酸序列。该蛋白的一级结构由283个氨基酸残基组成，其NH2末端序列Met-Ser-Pro-Val-Tyr-Ser与Edman降解酵母孔蛋白的结果一致，只是成熟蛋白中缺少引发子蛋氨酸。推导出的序列的总极性指数为46.3%，该值落在可溶性蛋白质的正常范围内。对蛋白质疏水性的评价表明，NH2末端的三分之一是相对亲水的，其余的分子相当疏水。一个有趣的发现是，酵母孔蛋白的NH2末端区域(由大约50个氨基酸残基组成)显示出类似于70-kd蛋白相应部分的结构特征，70-kd蛋白也是酵母线粒体膜外膜蛋白。我们推测，这个NH2末端序列，就像70kd蛋白的序列一样，是将孔蛋白靶向线粒体膜外所必需的。
We have cloned a full‐length cDNA for yeast porin, the major outer mitochondrial membrane protein from Saccharomyces cerevisiae, and determined its nucleotide sequence. The primary structure of the protein, deduced from the nucleotide sequence, consisted of 283 amino acid residues and its NH2‐terminal sequence, Met‐Ser‐Pro‐Pro‐Val‐Tyr‐Ser, coincided with that determined by Edman degradation for yeast porin, except that the initiator methionine was missing in the mature protein. The deduced sequence had an overall polarity index of 46.3%, a value which falls in the normal range for soluble proteins. An evaluation of hydropathy of the protein indicated that the NH2‐terminal one third was relatively hydrophilic and the rest of the molecule was rather hydrophobic. An interesting finding was that the NH2‐terminal region of yeast porin (consisting of some 50 amino acid residues) shows structural features that resemble those of the corresponding portion of 70‐kd protein, which is also a yeast outer mitochondrial membrane protein. We postulate that this NH2‐terminal sequence, like that of 70‐kd protein, is required for targeting the porin to the outer mitochondrial membrane.