TY - JOUR T1 - Properties of Ca++ release induced by puff adder lectin, a novel lectin from the snake Bitis arietans, in sarcoplasmic reticulum. JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 1043 LP - 1048 VL - 277 IS - 2 AU - M Ohkura AU - Y Miyashita AU - T Nikai AU - J Suzuki AU - Y Komori AU - H Sugihara AU - Y Ohizumi Y1 - 1996/05/01 UR - http://jpet.aspetjournals.org/content/277/2/1043.abstract N2 - Puff adder lectin (PAL), a novel lectin venom purified from Bitis arietans, induced Ca++ release from the heavy fraction (HSR) but not from the light fraction of skeletal muscle sarcoplasmic reticulum with EC50 congruent to 10 microM. The potency of PAL was approximately 200-fold higher than that of caffeine. The bell-shaped profile of Ca++ dependence for PAL was almost the same as that for myotoxin a (MYTX), a peptide Ca++ releaser, but was different from that for caffeine. Typical blockers of Ca++ release channels, such as Mg+2, procaine, ruthenium red and ryanodine, markedly reduced PAL-induced Ca++ release from HSR. Interestingly, PAL inhibited 125I-MYTX binding to HSR with IC50 approximately equal to 20 microM. Scatchard analysis revealed that the mode of inhibition by PAL was noncompetitive, which suggests that PAL binds to a different site from that of MYTX. PAL did not affect 3H-ryanodine binding to HSR. These results suggest that PAL binds to a different site from that of MYTX to cause Ca++ release from HSR with novel properties. ER -