title: Proteolysis and the domain organization of myosin subfragment 1.
abstract: Because the proteolytic cleavage of a folded polypeptide depends not only on the specificity of the protease but on the nature of the folding, we investigated the cleavage of (chymotryptically produced) subfragment 1 (designated "S-1") or "head" segment of myosin by seven proteases with different specificities. All seven produced approximately the same three fragments of S-1--namely, fragments (from the NH2 terminus) of 27, 50, and 20 kilodaltons, suggesting that in intact S-1 these fragments are distinct domains. The same proteases were used to hydrolyze the MgADP complex of S-1. All failed to do so except trypsin, which, as found earlier [Hozumi, T. (1983) Biochemistry 22, 799-804], makes two additional cleavages. This result suggests that the conformational change induced by MgADP opens up only a small stretch of polypeptide chain, which stretch happens to be vulnerable to trypsin.
mesh_terms: D000818:Animals; D003546:Cysteine Endopeptidases; D019286:Endopeptidase K; D010450:Endopeptidases / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D007700:Kinetics; D009132:Muscles / Q000378:metabolism; D015879:Myosin Subfragments; D009218:Myosins / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D012697:Serine Endopeptidases; D013329:Structure-Activity Relationship; D013381:Subtilisins / Q000378:metabolism; D013820:Thermolysin / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D015879:Myosin Subfragments; D010446:Peptide Fragments; D010450:Endopeptidases; D012697:Serine Endopeptidases; D013381:Subtilisins; C028344:glutamyl endopeptidase; D014357:Trypsin; D019286:Endopeptidase K; D005341:Fibrinolysin; D003546:Cysteine Endopeptidases; C019913:clostripain; D013820:Thermolysin; D009218:Myosins