title: A putative role for calmodulin in the activation of Neurospora crassa chitin synthase.
abstract: The possible role of calmodulin in cell wall formation and chitin synthesis was studied in Neurospora crassa by examining the effects of anti-calmodulin agents on protoplast regeneration and possible associations between chitin synthase and calmodulin related proteins in microsomal isolates. Protoplast regeneration was inhibited by trifluoperazine (> 20 microM), an anticalmodulin agent. Chitin synthase activity in microsomes was associated with that of calmodulin-dependent protein kinase and inhibited by trifluoperazine (100 microM). In vitro activity of chitin synthase was enhanced upon inclusion of calmodulin (300 ng) in the assay mix, 63% over and above the stimulation brought about by trypsin, an activator of the enzyme. Autoradiography studies on microsomal proteins revealed calmodulin-dependent phosphorylation of two microsomal calmodulin-binding proteins (106 and 89 kDa). The results indicate that calmodulin-mediated phosphorylation of specific microsomal proteins may be important in the in vivo activation of chitin synthase.
authors.affiliation: Department of Biochemistry, University College of Science, Osmania University, Hyderabad, India.
authors.forename: K
authors.initials: K
authors.lastname: Suresh
authors.forename: C
authors.initials: C
authors.lastname: Subramanyam
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002473:Cell Wall; D002614:Chelating Agents / Q000494:pharmacology; D002687:Chitin Synthase / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D008861:Microsomes / Q000201:enzymology; D009492:Neurospora crassa / Q000201:enzymology*; D010766:Phosphorylation; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D014268:Trifluoperazine / Q000494:pharmacology; D014357:Trypsin
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D002614:Chelating Agents; D014268:Trifluoperazine; D004533:Egtazic Acid; D002687:Chitin Synthase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D014357:Trypsin