Davis N G, Model P
Cell. 1985 Jun;41(2):607-14. doi: 10.1016/s0092-8674(85)80033-7.
A hydrophobic sequence of 23 contiguous, uncharged residues anchors the coliphage f1 gene III protein (pIII) to the Escherichia coli cytoplasmic membrane; mutations removing this domain allow secretion of the protein to the periplasm. Multiple copies of an oligonucleotide encoding the hydrophobic repeat, Leu-Ala-Leu-Val, were introduced into genes for secreted forms of pIII. Artificial domains of 16 or more hydrophobic residues function to anchor the protein. Pronase protection experiments demonstrate that the new sequences act to halt transfer of the protein across the membrane, thus specifying a transmembrane topology. Relocating the hydrophobic domain within the polypeptide chain predictably alters the resultant protein/membrane topology. Repeats of a polar sequence were inserted with no effect on secretion. Furthermore, an unrelated hydrophobic sequence, uncovered by a gene III frameshift mutation, acts to anchor the protein. We conclude that function simply reflects hydrophobicity and not some more subtle feature of structure or sequence.
一段由23个连续的不带电荷残基组成的疏水序列将大肠杆菌噬菌体f1的基因III蛋白（pIII）锚定在大肠杆菌细胞质膜上；去除该结构域的突变会使该蛋白分泌到周质中。编码疏水重复序列Leu-Ala-Leu-Val的寡核苷酸的多个拷贝被引入到pIII分泌形式的基因中。16个或更多疏水残基的人工结构域起到锚定该蛋白的作用。蛋白酶保护实验表明，新序列可阻止该蛋白跨膜转运，从而确定了跨膜拓扑结构。在多肽链内重新定位疏水结构域可预测地改变所得蛋白/膜的拓扑结构。插入极性序列的重复序列对分泌没有影响。此外，由基因III移码突变发现的一个不相关的疏水序列也起到锚定该蛋白的作用。我们得出结论，功能仅仅反映疏水性，而不是结构或序列的一些更微妙的特征。
