EXTRACELLULAR DOMAIN OF NEUROTROPHIN RECEPTOR TRKB - DISULFIDE STRUCTURE, N-GLYCOSYLATION SITES, AND LIGAND-BINDING

An extracellular domain of a human neurotrophin receptor trkB was expr essed in Chinese hamster ovary cells and isolated as a glycoprotein po ssessing binding activity for brain-derived neurotrophic factor. The e xtracellular domain contains 398 amino acids and has a molecular weigh t of 60.6 kDa according to laser desorption mass spectrometry, indicat ing that the extracellular domain of trkB contains 33.3% carbohydrate moieties. Six disulfide linkages were determined to be Cys1-Cys7, Cys5 -Cys14, Cys121-Cys145, Cys123-Cys163, Cys187-Cys235, and Cys271-Cys314 , respectively, Cys300 was detected as a free sulfhydryl residue, Cyst eine clusters 1 and 2 located in the N-terminal domain possess a simil ar type of disulfide structure and two other disulfide bonds in the C- terminal region are homologous to that of the Ig-like C2 domain. Among 12 potential N-linked glycosylation sites proposed in the soluble dom ain of trkB, 10 sites are actually glycosylated. (C) 1995 Academic Pre ss, Inc.