Thissen J A, Casey P J
Section of Cell Growth, Regulation, Duke University Medical Center, Durham, North Carolina 27710.
J Biol Chem. 1993 Jul 5;268(19):13780-3.
Prenylation and subsequent processing of many proteins involved in cellular signaling serves to direct and/or anchor these proteins to specific membranes in the cell. One major class of prenylated proteins contains the so-called CAAX motif; such proteins contain a cysteine residue fourth from the COOH terminus. After addition of the isoprenoid to this cysteine residue by specific cytosolic protein prenyltransferases, the proteins are subject to further processing by enzymes associated with microsomal membranes. This suggests that newly prenylated proteins are initially directed to a microsomal membrane compartment for completion of their processing. Using a radiolabeled, prenylated peptide as a ligand, we have identified a specific, high affinity binding site or receptor on microsomal membranes. This receptor is both protease- and heat-sensitive and exhibits saturable binding of the prenylated peptide with a KD of 30 nM. Competition analysis indicates that both geranylgeranylated and farnesylated, but not myristoylated, peptides bind to this receptor. A fully processed prenylated protein also does not compete, indicating a role for the three terminal residues of the prenylated peptide in receptor recognition. This receptor may serve to direct newly prenylated proteins to a microsomal compartment for completion of processing prior to trafficking to their final destination in the cell.
参与细胞信号传导的许多蛋白质的异戊二烯化及后续加工过程，有助于将这些蛋白质定向和/或锚定到细胞内的特定膜上。一类主要的异戊二烯化蛋白质含有所谓的CAAX基序；这类蛋白质在COOH末端的第四个位置含有一个半胱氨酸残基。在特定的胞质蛋白异戊二烯基转移酶将类异戊二烯添加到这个半胱氨酸残基上之后，这些蛋白质会受到与微粒体膜相关的酶的进一步加工。这表明新异戊二烯化的蛋白质最初被定向到微粒体膜区室以完成其加工。使用放射性标记的异戊二烯化肽作为配体，我们在微粒体膜上鉴定出了一个特异性的高亲和力结合位点或受体。该受体对蛋白酶和热敏感，并且对异戊二烯化肽表现出可饱和结合，解离常数为30 nM。竞争分析表明，香叶基香叶基化和法尼基化的肽，但肉豆蔻酰化的肽不与该受体结合。一个完全加工的异戊二烯化蛋白质也不竞争，这表明异戊二烯化肽的三个末端残基在受体识别中起作用。该受体可能有助于将新异戊二烯化的蛋白质定向到微粒体区室，以便在运输到细胞内的最终目的地之前完成加工。
