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 32,000-dalton protein (p32) located in avian retrovirus cores was immunoprecipitated from [35S]methionine-labeled avian myeloblastosis virus (AMV) propagated in cultured chicken embryo fibroblast cells by an antiserum preparation (sarc III) derived from tumor-bearing hamsters injected with cloned and passaged cells from an avian sarcoma virus-induced primary hamster tumor. Since sarc III serum apparently contained antibodies only to virus-coded proteins and not to chicken cellular proteins, the immunoprecipitation of p32 from AMV by sarc III serum strongly suggested that p32 is virus coded. The origin of p32 was more definitively established by demonstrating the existence of a structural relationship between p32 and the AMV DNA polymerase. AMV p32 cross-reacted with the beta polypeptide of AMV alphabeta DNA polymerase in radioimmunoprecipitation and radioimmunoprecipitation inhibition assays, indicating that p32 and beta share common antigenic determinants. This relationship was clarified by sodium do-decyl sulfate-polyacrylamide gel electrophoretic analysis of the peptides generated by limited proteolysis of 125I-labeled AMV DNA polymerase polypeptides and of 125I-labeled AMV p32 by chymotrypsin or Staphylococcus aureus V-8 protease. The peptides which appeared during proteolytic digestion of p32 were a subset of those produced by digestion of the beta polypeptide; however, p32 had no discernible peptides in common with the alpha polypeptide. Further, all of the peptides produced by limited proteolysis of beta were present in the digests of either p32 or alpha. Our findings suggest that p32 is apparently derived by cleavage of the beta polypeptide of AMV DNA polymerase, presumably at a site near or identical to that at which alpha is generated from beta by proteolytic cleavage.
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PMID:Virus-coded origin of a 32,000-dalton protein from avian retrovirus cores: structural relatedness of p32 and the beta polypeptide of the avian retrovirus DNA polymerase. 8 16

Calpactin, or calpactin heavy chain (p36), reconstitute secretion in digitonin-permeabilized adrenal chromaffin cells after a reduction in their secretory potential resulting from the loss of cytosolic components. We have characterized the stimulatory effect of p36, which resulted in an increase in both the extent and the rate of exocytosis. A mixture of other annexins (p70 and p32) did not have any effect on secretion at similar or greater concentrations than p36. Controlled proteolysis of p36 using chymotrypsin was carried out, and the 33,000 molecular weight core and 3000 molecular weight tail peptide isolated. In contrast to p36, p33 had no effect on exocytosis, even at high calcium concentrations. The N-terminal tail peptide and a synthetic peptide based on the tail of p36 [Ac-calpactin-(1-15)-NH2] had no effect on endogenous secretion, or secretion stimulated by exogenous p36. The results show that both the tail and core domains are required for p36 to stimulate exocytosis. The tail domain is unlikely to be required for interaction with cellular components but probably has a regulatory effect on the core domain. Endogenous secretion and the stimulatory effect of p36 were markedly inhibited by depletion of ATP. The ATP requirement for p36 action was not due to a requirement for phosphorylation by protein kinase C (PKC), since the PKC inhibitor staurosporine partially inhibited endogenous secretion but did not affect the stimulation of exocytosis due to exogenous p36.
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PMID:The stimulatory effect of calpactin (annexin II) on calcium-dependent exocytosis in chromaffin cells: requirement for both the N-terminal and core domains of p36 and ATP. 214 64