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)

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

p36 is a major substrate of both viral and growth factor-receptor-associated tyrosine protein kinases. p36 can be isolated as a complex consisting of a subunit of Mr 36,000 (p36) and a subunit of Mr 10,000 (p10), and it represents an abundant cellular protein. We have isolated the p36-p10 complex from bovine intestinal epithelium and analyzed the amino terminus of both subunits. Sequence analysis of the first 56 amino acids of p10 demonstrates a striking sequence homology (48% identically placed residues) with the Mr 10,000 calcium-binding proteins from bovine brain, termed S-100. Intestinal p36 could be effectively labeled on a single tyrosine in vitro with immunoprecipitated pp60v-src and [gamma-32P]ATP. Mild proteolysis of p36 with chymotrypsin resulted in the cleavage into large (Mr, 33,000) and small domains (Mr, 3000), with the latter representing the phosphorylated amino terminus. Although the amino terminus is apparently blocked, sequence analysis of a secondary tryptic peptide of the Mr 3000 fragment as well as the amino-terminal sequence of the Mr 33,000 domain and overlapping peptides clearly established the site of tyrosine phosphorylation.
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PMID:Amino-terminal sequence of p36 and associated p10: identification of the site of tyrosine phosphorylation and homology with S-100. 241 74

Microvilli isolated from the MAT-C1 ascites subline of the 13762 rat mammary adenocarcinoma contain a major calcium-sensitive microfilament-binding protein, AMV-p35 (ascites microvillar p35). Association of AMV-p35 with microfilament cores during Triton X-100 extraction of the microvilli is half-maximal at 0.1-0.2 mM calcium. The protein, which comprises 6% of the total microvillar protein, can be isolated from microfilament cores prepared in the presence of calcium by extraction with EGTA and purification by ion-exchange chromatography. Alternatively, the protein can be isolated from Triton extracts of microvilli prepared in the absence of calcium by precipitation with calcium, solubilization of the precipitate with EGTA, and chromatography on an ion-exchange column. AMV-p35 binds to phosphatidylserine liposomes and F-actin with half-maximal calcium concentrations of about 10 microM and 0.2 mM, respectively. Treatment of AMV-p35 with chymotrypsin yields a 33,000-dalton fragment, behavior similar to the tyrosine kinase substrates calpactins I and II and lipocortins I and II. Immunoblot analyses using antibodies directed against calpactin I, lipocortin I, and lipocortin II showed strong reactivity of AMV-p35 with anti-calpactin I and anti-lipocortin II, but little reactivity toward anti-lipocortin I. The close relationship between AMV-p35 and calpactin I was verified by amino acid sequence analyses of peptides isolated from cyanogen bromide digests of AMV-p35. By gel filtration and velocity sedimentation analyses purified AMV-p35 is a 35,000-dalton monomer. Moreover, AMV-p35 extracted directly from microvilli in Triton/EGTA also behaves as a 35,000-dalton menomer. These findings indicate that AMV-p35 is closely related to the pp60src kinase substrate calpactin I (p36). However, AMV-p35 occurs in the microvilli as a monomer rather than as the heterotetrameric calpactin found in several other cell types.
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PMID:Isolation of a calcium-sensitive, 35,000-dalton microfilament- and liposome-binding protein from ascites tumor cell microvilli: identification as monomeric calpactin. 296 74