Hancock J F, Cadwallader K, Paterson H, Marshall C J
Department of Haematology, Royal Free Hospital, London, UK.
EMBO J. 1991 Dec;10(13):4033-9. doi: 10.1002/j.1460-2075.1991.tb04979.x.
Mutational analysis of p21ras has shown that plasma membrane targeting requires the combination of a CAAX motif with a polybasic domain of six lysine residues or a nearby palmitoylation site. However, it is not known from these studies whether these signals alone target p21ras to the plasma membrane. We now show that these C-terminal sequences are sufficient to target a heterologous cytosolic protein to the plasma membrane. Interestingly, the key feature of the p21K-ras(B) polybasic domain appears to be a positive charge, since a polyarginine domain can function as a plasma membrane targeting motif in conjunction with the CAAX box and p21K-ras(B) with the polylysine domain replaced by arginines is biologically active. Since some ras-related proteins are modified by geranylgeranyl rather than farnesyl we have investigated whether modification of p21ras with geranylgeranyl affects its subcellular localization. Geranylgeranyl can substitute for farnesyl in combining with a polybasic domain to target p21K-ras(B) to the plasma membrane, but such geranylgeranylated proteins are more tightly bound to the membrane. This increased avidity of binding is presumably due to the extra length of the geranylgeranyl alkyl chain.
对p21ras的突变分析表明，质膜靶向需要CAAX基序与六个赖氨酸残基的多碱性结构域或附近的棕榈酰化位点相结合。然而，从这些研究中尚不清楚这些信号是否单独将p21ras靶向质膜。我们现在表明，这些C末端序列足以将异源胞质蛋白靶向质膜。有趣的是，p21K-ras(B)多碱性结构域的关键特征似乎是正电荷，因为聚精氨酸结构域可以与CAAX框一起作为质膜靶向基序，并且多赖氨酸结构域被精氨酸取代的p21K-ras(B)具有生物活性。由于一些与ras相关的蛋白质被香叶基香叶基化而不是法尼基化，我们研究了用香叶基香叶基对p21ras进行修饰是否会影响其亚细胞定位。香叶基香叶基可以在与多碱性结构域结合时替代法尼基，将p21K-ras(B)靶向质膜，但这种香叶基香叶基化的蛋白质与膜的结合更紧密。这种结合亲和力的增加可能是由于香叶基香叶基烷基链的额外长度。
