Role of cysteine residues in human plasma phospholipid transfer protein.

摘要: Phospholipid transfer protein (PLTP) belongs to a family of human plasma lipid proteins that bind small amphophilic molecules. PLTP contains cysteines at residues 5, 129, 168, and 318. Bactericidal/permeability-increasing protein, which is member the same gene family, an essential disulfide bond between Cys135 Cys175; these residues, correspond Cys129 Cys168 in PLTP, are conserved among all known members family. To identify importance remaining cysteine secretion activity, each was replaced by glycine site-directed mutagenesis. The mutant as well wild-type cDNAs were cloned into mammalian expression vector pSV·SPORT1, transfected COS-6 cells for expression. → Gly incompetent. Neither mass nor activity detectable cell lysates culture medium. Relative Cys5 Cys318 exhibited similar specific activities but partially impaired synthesis secretion. Intracellular appeared two bands 75 51 kDa corresponding reported molecular masses glycosylated nonglycosylated forms. medium, suggesting glycosylation does not affect activity.