Structural analyses of sugar chains from ricin A-chain variant.

Two glycopeptides were isolated from a tryptic digest of ricin A-chain variant by gel filtration and reversed-phase HPLC. Their amino acid compositions and sequences showed that Asn-10 and Asn-236 are glycosylated. The sugar chains were liberated from these glycopeptides by hydrazynolysis, N-acetylated, and pyridylaminated. Component analysis and comparison of elution positions of the purified pyridylamino (PA-) sugar chains with those of authentic PA-sugar chains from the major ricin A-chain by reversed-phase HPLC and size fractionation HPLC suggested that both sugar chains linked to Asn-10 and Asn-236 of the ricin A-chain variant are M3FX, identical to that linked to Asn-10 of the major ricin A-chain.