Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

High cell density and cell cycle withdrawal stimulate the differentiation of BC3H1 smooth muscle-like cells. The differentiation process is accompanied by extensive changes in cell shape and the increased expression of a variety of muscle-specific proteins including the vascular smooth muscle-specific isoform of the contractile protein, alpha-actin. Results of actin peptide map analyses described in this report now indicate that a second, sarcomeric muscle-specific alpha-actin isoform is expressed in serum-deprived BC3H1 myocytes and that the induction of this actin isoform occurs late in differentiation well after the observed upregulation of vascular alpha-actin synthesis. The sarcomeric alpha-actin was identified in myocytes on the basis of the unique electrophoretic mobility of its NH2-terminal tryptic peptide, the distribution of cleavage products that were obtained when the NH2-terminal tryptic peptide was subjected to secondary proteolytic cleavage with thermolysin and Staphylococcus aureus V8 protease, and the presence of an additional cysteine residue at the NH2 terminus of the biosynthetic precursor of this novel alpha-actin. While expression of vascular alpha-actin was stimulated when myoblasts reached confluence, a 6-day post-confluent treatment with serum-free medium was required to induce maximal expression of the sarcomeric alpha-actin. Blot hybridization analysis of total BC3H1 myocyte RNA using actin gene-specific cDNA probes indicated that the sarcomeric alpha-actin corresponds to the skeletal muscle-specific isoform. This is the first report describing dual expression of smooth muscle and sarcomeric muscle alpha-actins in a clonal myogenic cell line. The results indicate the potential usefulness of the BC3H1 cell line for studying relationships between divergent muscle alpha-actin gene sequences and transcriptional and translational controls during myogenesis.
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PMID:Sequential expression of smooth muscle and sarcomeric alpha-actin isoforms during BC3H1 cell differentiation. 247 Jul 44

Proteinase K, subtilisin, pronase E, elastase, bactotrypsin, and thermolysin are all shown here to cleave native mitochondrial creatine kinase from chicken heart (Mib-CK) very specifically at a single site, either before or after Ala-323. In analogy with hen egg ovalbumin, where the same proteases all cleaved the polypeptide chain very specifically around Ala-352, Ala-323 of Mib-CK may be located in an exposed surface loop that is sensitive to protease attack. Gel permeation chromatography demonstrated that the two proteolytic fragments of Mib-CK with M(r)'s of approximately 37,000 and approximately 6000 remain associated with each other. Proteinase K cleavage did not influence the octamer to dimer ratio of Mib-CK, indicating that selective cleavage after Ala-323 has no direct effect on dimer-dimer interfaces within the octamer. However, upon addition of MgADP plus creatine and nitrate to induce a transition-state analogue complex of the enzyme, native Mib-CK dissociated much more readily into dimers than proteinase K-digested Mib-CK. Furthermore, proteinase K cleavage of Mib-CK resulted in 2-11-fold decreases in the Vmax values, as well as in 6-23-fold increases in the Km values for phosphocreatine, creatine, and MgATP, whereas the Kd values for both MgATP and creatine were unaffected. Consequently, proteinase K cleavage of Mib-CK does not affect substrate binding per se, but interferes with substrate-induced conformational changes which are essential for catalysis and which mediate the synergism in substrate binding as it is observed with the unmodified enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Limited proteolysis of creatine kinase. Implications for three-dimensional structure and for conformational substrates. 839 19