Dai Q, Choy E, Chiu V, Romano J, Slivka S R, Steitz S A, Michaelis S, Philips M R
Departments of Medicine and Cell Biology, New York University School of Medicine, New York, New York 10016, USA.
J Biol Chem. 1998 Jun 12;273(24):15030-4. doi: 10.1074/jbc.273.24.15030.
Prenylcysteine carboxyl methyltransferase (pcCMT) is the third of three enzymes that posttranslationally modify C-terminal CAAX motifs and thereby target CAAX proteins to the plasma membrane. Here we report the molecular characterization and subcellular localization of the first mammalian (human myeloid) pcCMT. The deduced amino acid sequence of mammalian pcCMT predicts a multiple membrane-spanning protein with homologies to the yeast pcCMT, STE14, and the mammalian band 3 anion transporter. The human gene complemented a ste14 mutant. pcCMT mRNAs were ubiquitously expressed in human tissues. An anti-pcCMT antiserum detected a 33-kDa protein in myeloid cell membranes. Ectopically expressed recombinant pcCMT had enzymatic activity identical to that observed in neutrophil membranes. Mammalian pcCMT was not expressed at the plasma membrane but rather restricted to the endoplasmic reticulum. Thus, the final enzyme in the sequence that modifies CAAX motifs is located in membranes topologically removed from the CAAX protein target membrane.
异戊烯基半胱氨酸羧基甲基转移酶（pcCMT）是三种对C末端CAAX基序进行翻译后修饰从而将CAAX蛋白靶向质膜的酶中的第三种。在此，我们报告了首个哺乳动物（人类髓系）pcCMT的分子特征和亚细胞定位。哺乳动物pcCMT推导的氨基酸序列预测其为一种多跨膜蛋白，与酵母pcCMT、STE14以及哺乳动物带3阴离子转运体具有同源性。人类基因可互补ste14突变体。pcCMT mRNA在人类组织中广泛表达。一种抗pcCMT抗血清在髓系细胞膜中检测到一种33 kDa的蛋白质。异位表达的重组pcCMT具有与在中性粒细胞膜中观察到的相同的酶活性。哺乳动物pcCMT并非在质膜上表达，而是局限于内质网。因此，修饰CAAX基序序列中的最后一种酶位于拓扑结构上与CAAX蛋白靶膜分离的膜中。
