Contribution of the N-linked carbohydrate of erythrocyte antigen CD59 to its complement-inhibitory activity.

摘要: The contribution of N-linked carbohydrate to the complement-inhibitory function human erythrocyte membrane glycoprotein, CD59, was investigated. Amino acid sequence analysis tryptic peptides labeled with [3H]borohydride revealed an moiety at Asn18 residue. No O-linked detected, as judged by failure asialo-CD59 bind peanut agglutinin and its resistance digestion O-glycanase. apparent molecular mass CD59 reduced from 18-20 14 kDa upon complete N-glycanase, no detectable proteolysis. N-glycanase associated 88 +/- 4% loss activity protein, assessed capacity protect chicken erythrocytes lysis C5b-9 proteins. By contrast, change in observed after neuraminidase, under conditions that removed greater than 60% [3H]sialic residues. Despite functional digestion, we detected deglycosylated incorporate into membranes or specifically species selectivity C8 C9 components attack complex. In order alter branched-chain structure without enzymatic Chinese hamster ovary (CHO) cells transfected cDNA for were grown alpha-mannosidase inhibitor, 1-deoxymannojirimycin, resulting conversion approximately 70% glycoprotein a high mannose. When presence C5b-9-inhibitory expressed on surface CHO amount comparable digested protein. Taken together, these data suggest normal glycosylation is required expression surfaces, although sugar residues do not contribute CD59's affinity