Title : Complete localization of the
intrachain disulphide bonds and the N-glycosylation points in the
alpha-subunit of human platelet
glycoprotein IIb
Abstract :
- Glycoprotein IIb ( GPIIb ), one of the two molecular components of the inducible receptor for fibrinogen on the platelet surface, is formed from two subunits , GPIIb alpha (114 kDa) and GPIIb beta (22.5 kDa), joined by a single disulphide bond
- CNBr cleavage of GPIIb , together with tryptic or endoproteinase Lys-C digestion of some of the isolated CNBr peptides , followed by amino acid and N-terminal sequence analysis of the isolated fragments , allowed us to locate unambiguously all the unknown disulphide bonds and the N-glycosylation points in platelet GPIIb
- It could be established that each cysteine residue in GPIIb , beginning at alpha- Cys-56 , is disulphide-bonded to its nearest neighbour in the amino acid sequence
- Given the extensive structural similarity among the two-chain alpha- subunits of Arg-Gly-Asp adhesion receptors and the conservative positions of cysteine residues in their amino acid sequences , the intrachain and interchain disulphide-bond pattern found here in GPIIb will most probably be conserved in all two-chain alpha-subunits of these receptors
- The N-linked glycosylation points found here in platelet GPIIb are the same as the five N-glycosylated asparagine residues suggested after cDNA sequencing of human erythroleukaemic-cell GPIIb [Poncz, Eisman, Heindenreich, Silver, Vilaire, Surrey, Schwartz & Bennett (1987) J. Biol
- Chem
- 262, 8476-8482]
- Some of the general features of the structure of GPIIb , such as the existence of distinct domains in the alpha- and beta-subunits , as well as the identification of well-defined points in its external topography, are discussed