Wu H C, Hou C, Lin J J, Yem D W
Proc Natl Acad Sci U S A. 1977 Apr;74(4):1388-92. doi: 10.1073/pnas.74.4.1388.
A lipoprotein mutant of E. coli K-12 has been characterized. The mutant lipoprotein was found to differ from the wild-type lipoprotein in the following respects: (i) it is present in an appreciable amount in the soluble fraction (275,000 X g supernatant); (ii) it lacks the covalently-linked diglyceride; (iii) it contains an unmodified cysteine which can be carboxymethylated in vitro; (iv) it undergoes dimerization and the dimer can be converted into monomeric form by reduction with 2-mercaptoethanol; (v) both the monomeric form and especially the dimeric form of the mutant lipoprotein migrate more slowly than the corresponding forms of wild-type lipoprotein in sodium dodecyl sulfate/urea polyacrylamide gel electrophoresis; and (vi) the mutant lipoprotein is not assembled into the murein sacculi, and this results in a greatly reduced amount of bound-form lipoprotein in the mutant. These data strongly suggest that the mutation has affected the primary structure of lipoprotein, in such a way that it is not modified normally, leading to the production of a structurally-altered lipoprotein deficient in covalently-linked lipid as well as a defective assembly of the altered lipoprotein into the rigid layer of the cell envelope.
已对大肠杆菌K-12的一种脂蛋白突变体进行了表征。发现该突变体脂蛋白在以下方面与野生型脂蛋白不同：（i）它以可观的量存在于可溶部分（275,000×g上清液）中；（ii）它缺乏共价连接的甘油二酯；（iii）它含有一个未修饰的半胱氨酸，可在体外进行羧甲基化；（iv）它会发生二聚化，并且该二聚体可以通过用2-巯基乙醇还原转化为单体形式；（v）在十二烷基硫酸钠/尿素聚丙烯酰胺凝胶电泳中，突变体脂蛋白的单体形式尤其是二聚体形式的迁移速度比野生型脂蛋白的相应形式慢；以及（vi）突变体脂蛋白未组装到胞壁质囊中，这导致突变体中结合形式的脂蛋白数量大大减少。这些数据有力地表明，该突变影响了脂蛋白的一级结构，使其不能正常修饰，从而导致产生一种结构改变的脂蛋白，该脂蛋白缺乏共价连接的脂质，并且改变后的脂蛋白组装到细胞包膜的刚性层中存在缺陷。
