Blocks human Kv11.1/KCNH2/ERG1 potassium channels (reversible, IC(50)=3.4 nM) (PubMed:34201318). At high toxin concentrations, block of Kv11.1/KCNH2/ERG1 macroscopic current is almost complete (PubMed:34201318). Does not accelerate the kinetics of the closing process and has no effect on the activation and inactivation kinetics of the Kv11.1/KCNH2/ERG1 channels (PubMed:34201318). Expressed by the venom gland. Has the CSalpha/beta fold, which comprises one or two short alpha helices connected to anti-parallel beta-sheets stabilized by three or four disulfide bonds. Belongs to the ergtoxin family. Gamma-KTx 1 subfamily.