Ionomycin. Streptomyces conglobatus (Ca2+ Salt). Ionomycin, is a narrow spectrum antibiotic for Gram-positive bacteria, produced by Streptomyces conglobatus. In mammals cells ionomycin acts as a potent and selective Ca2+ ionophore, more effective than A23187. The enhancement of Ca2+ influx by Ionomycin, caused by direct stimulation of store-regulated cation entry and not by a direct action at the plasma membrane. Ionomycin induces hydrolysis of phosphoinositides, activation of PKC in human T cells and apoptosis in various cells lines. Cell Ca2+ Signaling; Ca2+ Ionophores.