Barber J R, Clarke S
J Biol Chem. 1984 Jun 10;259(11):7115-22.
S-Adenosyl-L-homocysteine was used to inhibit the methylation of carboxylic acid residues of membrane proteins in intact human erythrocytes. Incubation of erythrocytes for 24 h with 5 mM each of adenosine and L-homocysteine resulted in the intracellular accumulation of S-adenosyl-L-homocysteine and substantially inhibited membrane protein carboxyl methylation. From the degree of inhibition and from the observed turnover of methylated proteins, we estimate that the number of protein methyl esters in cells incubated with adenosine and L-homocysteine for 20 h is less than 20% that of cells incubated without these inhibitors. No significant differences in the physical deformability properties of the membrane of these hypomethylated cells were detected. However, there was a small but significant (p less than 0.001) increase in the amount of membrane protein D-aspartyl residues in these cells compared to control cells. These observations are consistent with the hypothesis that methylation of membrane proteins at D-aspartyl residues may result in the selective removal or repair of these uncommon residues.
S-腺苷-L-高半胱氨酸被用于抑制完整人红细胞中膜蛋白羧酸残基的甲基化。将红细胞与5 mM的腺苷和L-高半胱氨酸各孵育24小时，导致S-腺苷-L-高半胱氨酸在细胞内积累，并显著抑制膜蛋白羧基甲基化。根据抑制程度和观察到的甲基化蛋白的周转情况，我们估计，与腺苷和L-高半胱氨酸孵育20小时的细胞中蛋白质甲酯的数量不到未用这些抑制剂孵育的细胞的20%。未检测到这些低甲基化细胞的膜在物理变形性方面有显著差异。然而，与对照细胞相比，这些细胞中膜蛋白D-天冬氨酰残基的量有小幅但显著（p小于0.001）的增加。这些观察结果与以下假设一致，即膜蛋白在D-天冬氨酰残基处的甲基化可能导致这些不常见残基的选择性去除或修复。
