Binds irreversibly to M1 (CHRM1) muscarinic acetylcholine receptors, and reveals a slightly weaker effect on M3 (CHRM3) receptors. The mechanism of toxin-receptor interaction comprises at least two steps. The first step is fast with no competition between the toxin and the antagonist. The second step is slow with formation of a more stable toxin-receptor complex and inhibition of the antagonist binding. Monomer. Expressed by the venom gland. Has no effect on M2 (CHRM2) and M4 (CHRM4) receptors. Is classified as a P-type cytotoxin, since a proline residue stands at position 54 (Pro-31 in standard classification). Belongs to the snake three-finger toxin family. Short-chain subfamily. Aminergic toxin sub-subfamily.