Scheglmann Dietrich, Werner Knut, Eiselt Gabriele, Klinger Reinhard
Institute for Biochemistry II, Medical Faculty of the Friedrich Schiller University Jena, Nonnenplan 2, D-07743 Jena, Germany.
Protein Eng. 2002 Jun;15(6):521-8. doi: 10.1093/protein/15.6.521.
It is a well known phenomenon that the occurrence of several distinct amino acids at the C-terminus of proteins is non-random. We have analysed all Saccharomyces cerevisiae proteins predicted by computer databases and found lysine to be the most frequent residue both at the last (-1) and at the penultimate amino acid (-2) positions. To test the hypothesis that C-terminal basic residues efficiently bind to phospholipids we randomly expressed GST-fusion proteins from a yeast genomic library. Fifty-four different peptide fragments were found to bind phospholipids and 40% of them contained lysine/arginine residues at the (-1) or (-2) positions. One peptide showed high sequence similarity with the yeast protein Sip18p. Mutational analysis revealed that both C-terminal lysine residues of Sip18p are essential for phospholipid-binding in vitro. We assume that basic amino acid residues at the (-1) and (-2) positions in C-termini are suitable to attach the C-terminus of a given protein to membrane components such as phospholipids, thereby stabilizing the spatial structure of the protein or contributing to its subcellular localization. This mechanism could be an additional explanation for the C-terminal amino acid bias observed in proteins of several species.
蛋白质C末端出现几种不同氨基酸的现象并非随机，这是一个众所周知的现象。我们分析了计算机数据库预测的所有酿酒酵母蛋白质，发现赖氨酸是最后一个（-1）和倒数第二个氨基酸（-2）位置上最常见的残基。为了验证C末端碱性残基能有效结合磷脂的假设，我们从酵母基因组文库中随机表达了GST融合蛋白。发现54个不同的肽片段能结合磷脂，其中40%在（-1）或（-2）位置含有赖氨酸/精氨酸残基。一个肽与酵母蛋白Sip18p具有高度的序列相似性。突变分析表明，Sip18p的两个C末端赖氨酸残基对于体外磷脂结合至关重要。我们假设C末端（-1）和（-2）位置的碱性氨基酸残基适合将给定蛋白质的C末端附着于膜成分如磷脂上，从而稳定蛋白质的空间结构或有助于其亚细胞定位。这种机制可能是对几个物种蛋白质中观察到的C末端氨基酸偏好的另一种解释。
