A putative role for calmodulin in the activation of Neurospora crassa chitin synthase.
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.
Suresh
K
K
Department of Biochemistry, University College of Science, Osmania University, Hyderabad, India.
Subramanyam
C
C
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
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