title: The essentiality of B chain in stabilizing the structure of the A chain in beta 1-bungarotoxin from Bungarus multicinctus venom.
abstract: The dynamic of Trp residue in beta 1-bungarotoxin (beta 1-Bgt), the A chain of beta 1-Bgt and phospholipase A2 (PLA2) was assessed by fluorescence measurement. Acrylamide quenching studies showed that the exposure degree of the Trp in PLA2 is higher than the Trp in beta 1-Bgt. The Trp of beta 1-Bgt had a higher accessibility for iodide, reflecting that the basic nature of the B chain might exert an attractive electrostatic force for iodide and increase the susceptibility of Trp in the A chain to iodide. Removal of the B chain of beta 1-Bgt did not significantly affect the exposure degree of Trp in the A chain. Alternatively, the polarity of the environment around the Trp and the hydrophobic character of ANS and substrate binding sites in the separated A chain changed. Measurement of Trp fluorescence with increasing temperature showed that the stability of structure of beta 1-Bgt was higher than those of the separated A chain and PLA2. These results suggest that the B chain might interact with the A chain and stabilize the conformation of the A chain in beta 1-Bgt.
authors.affiliation: Department of Biochemistry, Kaohsiung Medical College, Taiwan, Republic of China.
authors.forename: L S
authors.initials: LS
authors.lastname: Chang
authors.forename: S R
authors.initials: SR
authors.lastname: Lin
authors.forename: C C
authors.initials: CC
authors.lastname: Chang
authors.forename: C C
authors.initials: CC
authors.lastname: Yang
mesh_terms: D000818:Animals; D002038:Bungarotoxins / Q000737:chemistry*; D017838:Bungarus; D010446:Peptide Fragments / Q000737:chemistry; D010741:Phospholipases A / Q000737:chemistry; D054467:Phospholipases A2; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013438:Sulfhydryl Compounds / Q000737:chemistry; D014364:Tryptophan / Q000032:analysis
chemical_list: D002038:Bungarotoxins; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds; D014364:Tryptophan; D010741:Phospholipases A; D054467:Phospholipases A2