Polymyxin B is a selective and potent antagonist of calmodulin.
Polymyxin B, a cyclic peptide antibiotic, is considered to be a rather selective antagonist of protein kinase C. This drug is therefore widely used to evaluate the involvement of protein kinase C in cellular processes. In the present study, we investigated the effects of polymyxin B on the activity of calmodulin-dependent cyclic 3':5'-nucleotide phosphodiesterase in vitro. The drug potently inhibited this enzyme (IC50 80 nM in the presence of 500 microM Ca2+), while about 200-fold higher concentrations were required to inhibit protein kinase C to the same extent. Phosphodiesterase inhibition was competitive with respect to Ca2+ and calmodulin. Evidence for the formation of a complex between polymyxin B and calmodulin was obtained by polyacrylamide gel electrophoresis under non-denaturing conditions, and by affinity chromatography of calmodulin on polymyxin B-agarose. We therefore suggest that, at least in vitro, polymyxin B is a potent and selective inhibitor of calmodulin.
Hegemann
L
L
Department of Neurobiology, Troponwerke GmbH & Co. KG, Cologne, F.R.G.
van Rooijen
L A
LA
Traber
J
J
Schmidt
B H
BH
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002417:Cattle; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000201:enzymology; D011112:Polymyxin B / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D002147:Calmodulin; D011493:Protein Kinase C; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D011112:Polymyxin B; D002118:Calcium