Minoshima S, Ohba M, Hayashi H
J Biochem. 1981 Feb;89(2):411-20. doi: 10.1093/oxfordjournals.jbchem.a133216.
An in vitro system for the methylation of methyl-accepting chemotaxis proteins (MCP's), which have been shown to be membrane integral proteins, was constructed. The system, consisting of the membrane, the cytoplasm, and labeled S-adenosyl methionine, showed the following characteristics. 1. The methylation of MCP in the membrane required the cytoplasm. The rate of incorporation of the labeled methyl group into MCP was dependent on the amount of the cytoplasm. 2. Incorporation of the labeled methyl moiety into MCP reached a steady state, and the level of the steady state incorporation was dependent on the concentration of the cytoplasm when the concentration of the membrane protein was constant. 3. The methyl moiety which had been incorporated into MCP before the steady state could be exchanged. It was suggested that the amount of methyl group introduced into MCP was equal to that of taken from MCP. 4. The methylated MCP was demethylated faster in the presence of a methyl donor than in its absence. 5. The membranes obtained from cheX-, cheB-, and cheZ mutants were inactive in the present in vitro system even when they were mixed with the wild type cytoplasm.
构建了一种用于甲基化甲基接受趋化蛋白（MCPs）的体外系统，MCPs已被证明是膜整合蛋白。该系统由膜、细胞质和标记的S-腺苷甲硫氨酸组成，具有以下特点：1. 膜中MCP的甲基化需要细胞质。标记甲基基团掺入MCP的速率取决于细胞质的量。2. 当膜蛋白浓度恒定时，标记甲基部分掺入MCP达到稳态，且稳态掺入水平取决于细胞质的浓度。3. 稳态前掺入MCP的甲基部分可以交换。提示引入MCP的甲基量与从MCP中去除的甲基量相等。4. 存在甲基供体时，甲基化的MCP去甲基化比不存在时更快。5. 从cheX、cheB和cheZ突变体获得的膜在当前体外系统中无活性，即使它们与野生型细胞质混合。
