Properties of Ca++ release induced by puff adder lectin, a novel lectin from the snake Bitis arietans, in sarcoplasmic reticulum.
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.
Ohkura
M
M
Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Miyashita
Y
Y
Nikai
T
T
Suzuki
J
J
Komori
Y
Y
Sugihara
H
H
Ohizumi
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003435:Crotalid Venoms / Q000378:metabolism; D037102:Lectins / Q000494:pharmacology*; D011817:Rabbits; D012433:Ryanodine / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D014757:Viper Venoms / Q000494:pharmacology*
D003435:Crotalid Venoms; D037102:Lectins; D014757:Viper Venoms; D012433:Ryanodine; C018932:myotoxin A; D002118:Calcium