Bizzozero O A, Good L K, Evans J E
Biochemistry Dept., E. K. Shriver Center, Waltham, MA 02254.
Biochem Biophys Res Commun. 1990 Jul 16;170(1):375-82. doi: 10.1016/0006-291x(90)91284-y.
Myelin proteolipid protein (PLP) contains covalently bound long-chain fatty acids. A large proportion of these acyl moieties are bound in thioester linkages, as demonstrated by alkylation of newly formed SH groups upon deacylation. To identify the Cys residue(s) involved in the thioester linkage(s), reduced and carboxyamidomethylated proteolipid protein was labeled with [14C]iodoacetamide upon deacylation with neutral hydroxylamine. The labeled protein was digested with trypsin or pepsin, and peptides analyzed by RP-HPLC. Identification of the isolated radioactive peptides by amino acid analysis, peptide sequencing and/or fast-atom bombardment-mass spectrometry revealed that Cys108 in the bovine PLP sequence is an acylated site. The sequence surrounding the palmitoylation site in the myelin PLP is strikingly similar to that found in rhodopsin. Furthermore, as in rhodopsin and other members of the G protein-coupled receptor family, this Cys residue is located within a hydrophilic, basic, and possibly cytoplasmic, domain.
髓鞘蛋白脂蛋白（PLP）含有共价结合的长链脂肪酸。这些酰基部分很大一部分以硫酯键结合，脱酰作用后新形成的SH基团烷基化证明了这一点。为了鉴定参与硫酯键的半胱氨酸残基，在用中性羟胺脱酰后，用[14C]碘乙酰胺标记还原并羧酰胺甲基化的蛋白脂蛋白。将标记的蛋白质用胰蛋白酶或胃蛋白酶消化，并用反相高效液相色谱法分析肽段。通过氨基酸分析、肽测序和/或快原子轰击质谱法鉴定分离出的放射性肽，结果表明牛PLP序列中的半胱氨酸108是一个酰化位点。髓鞘PLP中棕榈酰化位点周围的序列与视紫红质中的序列惊人地相似。此外，与视紫红质和G蛋白偶联受体家族的其他成员一样，这个半胱氨酸残基位于一个亲水、碱性且可能是胞质的结构域内。
