Title : Epitopic structure of
Tn glycophorin A for an anti-Tn antibody (MLS 128)
Abstract :
- Glycophorin A was digested with glycoprotease (Pasteurella haemolytica) and the digest was fractionated by a combination of high-pressure column chromatographies to produce the glycopeptides GPA-1 to GPA-6
- Sequence analysis of the glycopeptides revealed that two serine residues ( Ser-14 and Ser-15 ) are not glycosylated, Thr-17 and Ser-19 being glycosylated instead, in disagreement with the accepted structure
- The glycopeptides thus obtained were treated with sialidase and beta-galactosidase
- The Tn antigenicity, as assayed by the binding to a monoclonal anti-Tn antibody (MLS 128), was found exclusively in the glycopeptides including three (cluster I) or four (cluster II) consecutive residues of GalNAc-Ser/Thr, whereas the glycopeptide ( GPA-2 ) containing two nonconsecutive GalNAc-Ser/Thr residues had practically no Tn antigenicity
- The immunoreactivities of GPA-1 and GPA-3, containing both clusters I and II, and GPA-4, containing cluster II, were 63% (calcd
- 67%), 81% (calcd
- 86%), and 50% (calcd
- 50%), respectively, of the immunoreactivity of GPA-5 or GPA-6, containing cluster I (the average being taken as the basis), based on the reactivity per GalNAc residue.
- These results indicate that clusters I and II react with the antibody to the same extent
- The structure consisting of three consecutive glycosylated Ser/Thr residues may be essential for Tn antigenicity in the light of previous results for ovine submaxillary mucin