Heterodimer: RV-4/RV-7 targets the presynaptic sites of the neuromuscular junction. Monomer: snake venom phospholipase A2 (PLA2) RV-7 that has low enzymatic activity and is not toxic. It inhibits the enzymatic activity of RV-4 in vitro but potentiates its lethal potency and neurotoxicity. It may facilitate the specific binding of RV-4 to its presynaptic binding sites, probably by acting as a chaperone, minimizing distraction and destruction of RV-4 en route to the site of action by reducing non-specific binding to muscle and other organs. PLA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) Binds 1 Ca(2+) ion. Heterodimer of a weakly toxic basic protein having phospholipase A2 activity (RV-4) and a non-toxic acidic protein which inhibits its enzymatic activity but potentiates its lethal potency and neurotoxicity (RV-7). Expressed by the venom gland. Belongs to the phospholipase A2 family. Group II subfamily. D49 sub-subfamily.