Post‐translational modification of the β‐subunit of the human fibronectin receptor

Abstract
Monoclonal antibody DH12, directed against the β‐subunit of the fibronectin receptor recognizes a doublet of proteins (100 and 110 kDa) in Western blots of solubilized whole fibroblasts. Pulse‐chase experiments with [35S]methionine in human skin fibroblasts suggested that the two proteins might be metabolically related as precursor (100 kDa) and product (110 kDa). Endo H digestion and [3H]fucose labeling suggested that maturation converted the high‐mannose oligosaccharides (100 kDa) to the endoglycosidase H resistant complex type (110 kDa). This was supported by N‐glycanase digestion and by chemical deglycosylation which showed a single polypeptide. Surface iodination of intact cells labeled only the presumed mature β‐subunit.