Gramicidin A is a peptide component of gramicidin, an antibiotic mixture originally isolated from B. brevis. Gramicidin A is a highly hydrophobic channel-forming ionophore that forms channels in model membranes that are permeable to monovalent cations. It induces degradation of hypoxia inducible factor 1 α (HIF-1α) in HEK293 cells and reduces growth in a human renal cell carcinoma mouse xenograft model when administered at a dose of 0.22 mg/kg three times per week. Gramicidin A has commonly been used to study channel structure and function.