rab GTP-binding proteins with three different carboxyl-terminal cysteine motifs are modified in vivo by 20-carbon isoprenoids.
rab GTP-binding proteins with three different carboxyl-terminal cysteine motifs are modified in vivo by 20-carbon isoprenoids.
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DOI：
10.1016/s0021-9258(19)50616-0
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发表时间：
1992-02
期刊：
影响因子：
--
通讯作者：
B. Kinsella;W. Maltese
中科院分区：
文献类型：
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作者：
B. Kinsella;W. Maltese
p21 ras和几种其它ras相关的GTP结合蛋白通过在保守的羧基末端序列基序Caa（M/S/L）内的半胱氨酸上添加15-碳法尼基或20-碳香叶基香叶基类异戊二烯进行后修饰，其中a是脂肪族氨基酸。以M或S结尾的蛋白质是法尼基转移酶的底物，而以L结尾的蛋白质优先被香叶基香叶基转移酶修饰。我们最近报道了由rab 1B（GGCC），rab 2（GGCC）和rab 5（CCSN）编码的GTP结合蛋白在体外翻译时被[3 H]甲羟戊酸的20-碳异戊二烯衍生物修饰，尽管具有不同于Caa（M/S/L）基序的羧基末端序列。我们现在表明，这些蛋白质的功能作为特定受体的香叶基香叶基在体外和修改的20-碳异戊二烯基团在COS细胞代谢标记[3 H]甲羟戊酸。由rab 4和rab 6编码的蛋白质，具有另一个不同的羧基末端基序（xCxC），在体外和体内被20-碳类异戊二烯类似地修饰。rab 5蛋白的牛儿基牛儿基修饰（CCSN）由脑胞液中的酶催化，但不由纯化的牛儿基牛儿基转移酶催化，所述纯化的牛儿基牛儿基转移酶修饰具有CaaL基序的GTP结合蛋白。与具有Caa（M/S/L）末端的蛋白质的异戊烯化不同，rab 5蛋白质的异戊烯化不被基于其羧基末端序列（TRNQCCSN）的合成肽抑制。当细胞类异戊二烯合成通过用洛伐他汀处理细胞而被阻断时，通常定位于内质网、高尔基体和核内体的膜中的rab蛋白在胞质溶胶中积累。通过向细胞提供甲羟戊酸，rab蛋白定位的这种变化被逆转。这些研究结果表明，geranylgeranyl修改的基础rab GTP结合蛋白与细胞内膜，在那里他们被假定为泡状交通介质的功能的能力。
p21ras and several other ras-related GTP-binding proteins are modified post-translationally by addition of 15-carbon farnesyl or 20-carbon geranylgeranyl isoprenoids to cysteines within a conserved carboxyl-terminal sequence motif, Caa(M/S/L), where a is an aliphatic amino acid. Proteins ending with M or S are substrates for farnesyltransferase, whereas those ending with L are modified preferentially by geranylgeranyltransferase. We recently reported that GTP-binding proteins encoded by rab1B (GGCC), rab2 (GGCC), and rab5 (CCSN) are modified by 20-carbon isoprenyl derivatives of [3H]mevalonate when translated in vitro, despite having carboxyl-terminal sequences distinct from the Caa(M/S/L) motif. We now show that these proteins function as specific acceptors for geranylgeranyl in vitro and are modified by 20-carbon isoprenyl groups in COS cells metabolically labeled with [3H]mevalonate. Proteins encoded by rab4 and rab6, with yet another distinct carboxyl-terminal motif (xCxC), are similarly modified by 20-carbon isoprenoids in vitro and in vivo. The geranylgeranyl modification of rab5 protein (CCSN) is catalyzed by an enzyme in brain cytosol but not by a purified geranylgeranyltransferase that modifies GTP-binding proteins with the CaaL motif. Unlike the prenylation of proteins with Caa(M/S/L) termini, the prenylation of rab5 protein is not inhibited by a synthetic peptide based on its carboxyl-terminal sequence (TRNQCCSN). When cellular isoprenoid synthesis is blocked by treatment of cells with lovastatin, rab proteins that are normally localized in membranes of the endoplasmic reticulum, Golgi apparatus, and endosomes accumulate in the cytosol. This change in rab protein localization is reversed by providing cells with mevalonate. These findings suggest that geranylgeranyl modification underlies the ability of rab GTP-binding proteins to associate with intracellular membranes, where they are postulated to function as mediators of vesicular traffic.