Evidence for the Occurrence of, and Possible Physiological Role for, Cyanobacterial Calmodulin

Abstract

Phosphate uptake by the blue-green alga Oscillatoria limnetica Lemmerman is stimulated by micromolar concentrations of Ca(2+). The calmodulin antagonists 4-(3-[2(trifluoromethyl)phenylthiazin-10-yl]propyl)-1-piperazine ethanol-HCl and its monofluoro-analog inhibit orthophosphate uptake of Oscillatoria limnetica by over 97% implying involvement of calmodulin in this process. A calmodulin-like protein was quantitated in cell-free extracts from O. limnetica by radioimmunoassay.