title: Isolation and characterization of a presynaptic neurotoxin, P-elapitoxin-Bf1a from Malaysian Bungarus fasciatus venom.
abstract: Presynaptic neurotoxins are one of the major components in Bungarus venom. Unlike other Bungarus species that have been studied, β-bungarotoxin has never been isolated from Bungarus fasciatus venom. It was hypothesized that the absence of β-bungarotoxin in this species was due to divergence during evolution prior to evolution of β-bungarotoxin. In this study, we have isolated a β-bungarotoxin isoform we named P-elapitoxin-Bf1a by using gel filtration, cation-exchange and reverse-phase chromatography from Malaysian B. fasciatus venom. The toxin consists of two heterogeneous subunits, subunit A and subunit B. LCMS/MS data showed that subunit A was homologous to acidic phospholipase A2 subunit A3 from Bungarus candidus and B. multicinctus venoms, whereas subunit B was homologous with subunit B1 from B. fasciatus venom that was previously detected by cDNA cloning. The toxin showed concentration- and time-dependent reduction of indirect-twitches without affecting contractile responses to ACh, CCh or KCl at the end of experiment in the chick biventer preparation. Toxin modification with 4-BPB inhibited the neurotoxic effect suggesting the importance of His-48. Tissue pre-incubation with monovalent B. fasciatus (BFAV) or neuro-polyvalent antivenom (NPV), at the recommended titer, was unable to inhibit the twitch reduction induced by the toxin. This study indicates that Malaysian B. fasciatus venom has a unique β-bungarotoxin isoform which was not neutralized by antivenoms. This suggests that there might be other presynaptic neurotoxins present in the venom and there is a variation in the enzymatic neurotoxin composition in venoms from different localities.
authors: Monash Venom Group, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia; Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia; Department of Basic Medical Sciences, Kulliyyah of Pharmacy, International Islamic University Malaysia, Pahang, Malaysia.
authors: Muhamad Rusdi Ahmad
authors: MR
authors: Rusmili
authors: Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia.
authors: Tee Ting
authors: TT
authors: Yee
authors: Department of Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors: Mohd Rais
authors: MR
authors: Mustafa
authors: Monash Venom Group, Faculty of Medicine, Nursing and Health Sciences, Monash University, Victoria, Australia.
authors: Wayne C
authors: WC
authors: Hodgson
authors: Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia. Electronic address: iekhsan.othman@monash.edu.
authors: Iekhsan
authors: I
authors: Othman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000997:Antivenins / Q000494:pharmacology; D002038:Bungarotoxins / Q000302:isolation & purification* / Q000494:pharmacology*; D017838:Bungarus; D002645:Chickens; D004546:Elapid Venoms / Q000737:chemistry*; D008296:Malaysia; D008297:Male; D008969:Molecular Sequence Data; D009469:Neuromuscular Junction / Q000187:drug effects; D009498:Neurotoxins / Q000302:isolation & purification* / Q000494:pharmacology*; D054467:Phospholipases A2 / Q000378:metabolism; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013785:Thailand
chemical_list: D000997:Antivenins; D002038:Bungarotoxins; D004546:Elapid Venoms; D009498:Neurotoxins; D054467:Phospholipases A2
keywords: Antivenom; Bungarus fasciatus; Chick biventer; Presynaptic neurotoxin; Purification; Snake venom