Q; How can a glycoprotein be Endo H-resistant ?

[Kernee H. Chang]

Dear GlycoFriends,

I've seen from the paper(Lodish et al, J.Biol.Chem., 1993, 268, 13639-49)

that a glycoprotein happen to be Endo H-resistant type, even though it 

has N-linked oligosaccharide.        Could this happen because of some 

structural hinderance or something else..?


Thank You !!