Collismycin A is a bacterial metabolite originally isolated from Streptomyces that has diverse biological activities, including antibacterial, antiproliferative, and neuroprotective properties. It is active against a variety of bacteria (MICs = 6.25 and 100 µg/ml) and fungi (MICs = 12.5-100 µg/ml). It inhibits proliferation of A549 lung, HCT116 colon, and HeLa cervical cancer cells (IC50s = 0.3, 0.6, and 0.3 µM, respectively) and NIH373 fibroblasts (IC50 = 56.6 µM) but not MDA-MD-231 breast cancer cells (IC50 = >100 µM). Collismycin A forms a complex with Fe(II) and Fe(III) at a 2:1 ratio, and the addition of iron ions inhibits the antiproliferative effect of collismycin A on HeLa cells, an effect that does not occur with the addition of zinc, manganese, copper, or magnesium ions. Collismycin A (1 µM) prevents apoptosis in the brain region of zebrafish larvae by 44% in a model of neuronal cell death induced by all-trans retinoic acid .