A collagen-binding protein involved in the differentiation of myoblasts recognizes the Arg-Gly-Asp sequence.
We had earlier demonstrated that a 46-kDa glycoprotein is involved in the differentiation of rat skeletal myoblasts. We now show that the binding of this glycoprotein to collagen and gelatin is disrupted by Arg-Gly-Asp (RGD) containing peptide but not by Arg-Gly-Glu (RGE). The former peptide also selectively elutes the 46-kDa glycoprotein bound to gelatin-Sepharose. Since all other proteins which bind RGD sequences have been found at the cell surface, we attempted to localize the 46-kDa glycoprotein by means of immuno fluorescent staining and radioiodine labeling. Surprisingly, the majority of the protein was found to be localized in the endoplasmic reticulum. Protease treatment of a microsomal fraction revealed that the protein is in the interior of the reticulum. Immunoprecipitation experiments, using a polyclonal antibody against the 46-kDa protein, demonstrated that no closely related proteins exist in myoblasts and also confirmed that the protein was not a fragment of a cell-surface localized protein. These findings suggest that the RGD sequence is also used in protein recognition within the cell.
Nandan
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Department of Biochemistry, Faculty of Medicine, University of Western Ontario, London, Canada.
Cates
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GA
Ball
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Sanwal
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BD
D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation; D008970:Molecular Weight; D009132:Muscles / Q000166:cytology*; D009842:Oligopeptides / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D038981:Receptors, Collagen; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D009842:Oligopeptides; D011956:Receptors, Cell Surface; D038981:Receptors, Collagen; C047981:arginyl-glycyl-aspartic acid; C046617:arginyl-glycyl-aspartyl-serine