Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A filamentous protein was isolated from crayfish claw muscle. This protein had physiochemical properties very similar to vertebrate skeletal muscle connectin (titin), although its apparent molecular mass (approximately 1200 kDa) was considerably lower than that of connectin (approximately 3000 kDa). Polyclonal as well as monoclonal antibodies against chicken skeletal muscle connectin reacted with the 1200 kDa protein from crayfish claw muscle. Conversely, polyclonal antibodies against crayfish 1200 kDa protein cross-reacted with chicken connectin. Circular dichroic spectra indicated the abundance of beta-sheet structure (approximately 60%). Low-angle shadowed images showed filamentous structures (0.2-0.5 microns) by electron microscopy. Proteolysis of the 1200 kDa protein by alpha-chymotrypsin or V8 protease rapidly resulted in formation of 1000 kDa or 1100 and 800 kDa peptides. The amino acid composition was very similar to those of vertebrate connectins and of honeybee flight muscle projectin. Based on the molecular weight and amino acid composition, the 1200 kDa protein is regarded to be crayfish projectin. Immunofluorescence and immunoelectron microscopy revealed that crayfish projectin was localized in the A/I junction area and A-band except for its centre region in crayfish claw muscles. Polyclonal antibodies against crayfish claw muscle projectin reacted with 1200 kDa projectin of honeybee and beetle flight muscle. A monoclonal antibody against chicken skeletal muscle connectin also reacted with honeybee and beetle projectin. Immunoelectron microscopic observations revealed that anti-crayfish projectin antibodies bound the connecting filaments linking the Z-line and the thick filaments up to the M-line of honeybee muscle sarcomere. Anti-crayfish projectin antibodies bound the I-band region near the Z-line of beetle flight muscle. It is concluded that the 1200 kDa projectin from crayfish claw muscle is an invertebrate connectin (titin). Recent work with locust flight muscle mini-titin (Nave & Weber, 1990) is in good agreement with the present study, except that the isolated mini-titin estimated as 600 kDa appears to be a proteolytic product (approximately 1100 kDa) of the parent molecule (approximately 1200 kDa).
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PMID:Projectin is an invertebrate connectin (titin): isolation from crayfish claw muscle and localization in crayfish claw muscle and insect flight muscle. 208 47

It has recently been shown that a monoclonal antibody SM 1-36-2 against connectin, an elastic filament of striated muscles, binds to the "elastic" domain of the molecule, and that the H subunit of neurofilament (NF-H), an intermediate filament of nerve cells, shares a homologous domain (Shimizu, T. et al. (1988) Biomed. Res. 9, 227-234 and Itoh, Y. et al. (1988) J. Biochem. 104, 504-508). In order to characterize (1) the intramolecular localization of the domain in the NF-H and (2) the effect of the phosphorylation state on the immunoreactivity, the homologous domain in the NF-H was analyzed by Western blotting after limited digestion with trypsin or alpha-chymotrypsin and dephosphorylation with E. coli alkaline phosphatase. It was found that (1) the epitope was located not in the core region but in the carboxyl-terminal peripheral (cross-bridge) region of NF-H and (2) the epitopes in connectin and NF-H were not affected by the phosphorylation state.
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PMID:The immunological homology between two filamentous cross-linker phosphoproteins, connectin and cross-bridge region of neurofilament-H, is not affected by the phosphorylation state. 272 66

Proteolytic fragments of 400 kD isolated from chymotrypsin-treated connectin, a muscle elastic protein, still retained the ability to cause aggregation of myosin filaments but lost the actin-bundling action. Tryptic digests of connectin showed similar effects. However, when connectin was hydrolyzed by pepsin to peptides smaller than approximately 40 kD, no such action was seen for both myosin and actin filaments. It is suggested that the actin bundling action of connectin filaments is due to topological restrictions. A modified reproducible procedure for the preparation of native connectin from chicken breast muscle is described in detail.
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PMID:Proteolytic fragments of connectin cause aggregation of myosin filaments but not of actin filaments. 644 94

The effects of various proteolytic enzymes on the high molecular weight protein (connectin) present in a direct sodium dodecyl sulfate extract of myofibrils from chicken breast muscle were studied in detail. To keep the high molecular weight proteins intact, myofibrils had to be prepared in the presence of EGTA. Trypsin, chymotrypsin, papain, and nagarse readily hydrolyzed connectin (doublet band of titin) and the band 3 protein (N2-line protein). Pepsin did not attack connectin, but digested the band 3 protein and myosin. Calcium-activated neutral proteinase hydrolyzed the band 3 protein, leaving connectin intact. On the other hand, serine protease digested connectin but not the band 3 protein.
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PMID:Connectin, an elastic protein of muscle. Effects of proteolytic enzymes in situ. 702 43