Natural human tumor necrosis factor beta (lymphotoxin). Variable O-glycosylation at Thr7, proteolytic processing, and allelic variation.

Natural human tumor necrosis factor beta (TNF-beta) purified from supernatants of a human B-lymphoblastoid cell line was found to be heterogeneous in molecular mass, with seven components resolved by gel electrophoresis. All components are N-glycosylated at Asn62; N-glycosylation does not contribute to heterogeneity. In addition, part of the molecules are O-glycosylated at Thr7; O-glycosylation is heterogeneous due to variable decoration with neuraminic acid. The four lower molecular mass forms are derived from the full-length protein by trypsin-like proteolytic cleavage in the N-proximal region; these clipped molecules lack O-linked carbohydrates. Two allelic variants differing in amino acid position 26 (threonine/asparagine) were identified.