This three-finger cytotoxin is a basic protein that interacts and penetrates into the cell membrane, with the tips of all the three loops. Cytotoxins which have a 'Pro-30' (P-type) interacts with membrane stronger that those which have a Ser-28 (S-type). CTI interacts with membrane weaker than CTII. Monomer in solution; Homodimer and oligomer in the presence of negatively charged lipids forming a pore with a size ranging between 20 and 30 Angstroms. Expressed by the venom gland. Is classified as a S-type cytotoxin, since a serine residue stands at position 27 (Ser-29 in standard classification). Belongs to the snake three-finger toxin family. Short-chain subfamily. Type IA cytotoxin sub-subfamily.