title: Both A chain and B chain of beta-bungarotoxin are functionally involved in the facilitation of spontaneous transmitter release in Xenopus nerve-muscle cultures.
abstract: In the present study, Xenopus nerve-muscle cultures were used to explore the functional roles of A chain (a phospholipase A(2) subunit) and B chain (a non-phospholipase A(2) subunit) of Bungarus multicinctus beta-bungarotoxin. It was found that beta-bungarotoxin induced an increment of the frequency of spontaneous synaptic currents (SSCs) in the nerve-muscle cultures. Modification of beta-bungarotoxin with pyridoxal-5'-phosphate or substitution of Ca(2+) with Ba(2+) in buffer abolished the phospholipase A(2) activity of beta-bungarotoxin and the facilitatory phase of SSC as well. Antibodies that were directed specifically against A chain or B chain effectively inhibited phospholipase A(2) activity, and as a consequence the SSC frequency was not greatly different from the control rate. These results suggest that both A and B chains are indispensable parts of beta-bungarotoxin for inducing the facilitation of SSC frequency with Xenopus nerve-muscle cultures.
authors.affiliation: Department of Biological Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC.
authors.forename: Jau-Cheng
authors.initials: JC
authors.lastname: Liou
authors.forename: Yun-Ching
authors.initials: YC
authors.lastname: Cheng
authors.forename: Kai-Hsiang
authors.initials: KH
authors.lastname: Kang
authors.forename: Yuan-Ping
authors.initials: YP
authors.lastname: Chu
authors.forename: Chen-Chung
authors.initials: CC
authors.lastname: Yang
authors.forename: Long-Sen
authors.initials: LS
authors.lastname: Chang
mesh_terms: D000818:Animals; D002038:Bungarotoxins / Q000276:immunology / Q000494:pharmacology*; D017838:Bungarus; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation*; D009469:Neuromuscular Junction / Q000187:drug effects*; D009498:Neurotoxins / Q000494:pharmacology*; D010741:Phospholipases A / Q000032:analysis / Q000037:antagonists & inhibitors / Q000276:immunology; D014981:Xenopus
chemical_list: D002038:Bungarotoxins; D009498:Neurotoxins; D010741:Phospholipases A