Protease resistance of the beta subunit of the hamster fibronectin receptor. Evidence for differential cleavage of membrane-bound and soluble receptor.
The structural stability of the hamster fibronectin receptor has been studied using limited proteolytic digestion and anti-(fibronectin receptor) monoclonal antibodies of known specificity. Treatment of the solubilized intact receptor or of the dissociated alpha and beta chains with any one of several proteases generated large protease-resistant fragments (92-110 kDa). Western blot analysis of tryptic digests using subunit-specific monoclonal antibodies revealed the large trypsin-generated fragment to be of beta-subunit origin. No products from the alpha subunit were detected. The protease-resistant fragment is lost upon exposure to reducing conditions; thus, the highly disulfide-bonded region of the beta subunit is important in the maintenance of the tertiary structure of the entire subunit. In contrast to solubilized fibronectin receptor, membrane-bound receptor is much more stable to proteolysis, and tryptic cleavage results in two large immunoreactive fragments of approximately 100 kDa and 95 kDa. This suggests a difference in the conformation and/or oligomeric organization of the membrane-bound receptor as compared with the solubilized heterodimeric receptor.
Sczekan
M M
MM
Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill 27599-7365.
Juliano
R L
RL
D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D003600:Cytosol / Q000276:immunology; D005353:Fibronectins / Q000378:metabolism*; D015151:Immunoblotting; D007700:Kinetics; D010446:Peptide Fragments / Q000302:isolation & purification; D010447:Peptide Hydrolases / Q000378:metabolism*; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000378:metabolism*; D012995:Solubility; D014357:Trypsin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D005353:Fibronectins; D010446:Peptide Fragments; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic; D010447:Peptide Hydrolases; D014357:Trypsin