Blocks M2 muscarinic acetylcholine receptors (CHRM2). Fully blocks the binding of N-methylscopolamine (NMS) and oxotremorine-M to M2 receptors, slightly increased NMS binding to M1 receptors. Monomer. Expressed by the venom gland. Has no effect on M3, M4 and M5 muscarinic acetylcholine receptors. Belongs to the snake three-finger toxin family. Short-chain subfamily. Type B muscarinic toxin sub-subfamily.