Antibody BCF2 against scorpion toxin Cn2 from Centuroides noxius Hoffmann: primary structure and three-dimensional model as free Fv fragment and complexed with its antigen.
The antibody BCF2 generated against the mammal-specific toxin Cn2 of the scorpion Centuroides noxius Hoffmann neutralizes the effect of both the toxin and the venom. We cloned and sequenced the genes coding for the Fv fragment of BCF2. A three-dimensional (3D) model of the Fv fragment was generated using a knowledge-based approach. Furthermore, a 3D model of the complex Cn2-BCF2 was built using the nuclear magnetic resonance (NMR) structure of Cn2 and experimental results on a putative epitope region around the N and C termini. The initial complex conformations were submitted to a new refinement procedure of rigid-body energy minimization combined with flexible-side-chain molecular dynamics. The final complex, selected after an extensive evaluation, uses the loop 7-11 as the central part of the epitope. The generated complex allows the following conclusions: 1) the neutralizing capacity of BCF2 toward the venom of C. noxius might rather be caused by the high venom concentration and toxicity of Cn2 than by a broad specificity, 2) the region involved in the binding of Cn2 to the Na(+) channel, should overlap with the employed epitope region, and 3) contact residues SerL91, AsnL92, LeuH50, AspH56, TyrH95, and TyrH98 of BCF2 are candidates for mutations to broaden its specificity. Proteins 1999;37:130-143.
Selisko
B
B
Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, National Autonomous University of Mexico (UNAM), Cuernavaca, Mexico.
Licea
A F
AF
Becerril
B
B
Zamudio
F
F
Possani
L D
LD
Horjales
E
E
D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D000937:Antigen-Antibody Reactions; D001483:Base Sequence; D003198:Computer Simulation; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D007128:Immunoglobulin Fragments / Q000737:chemistry / Q000276:immunology*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000276:immunology*; D011487:Protein Conformation; D012604:Scorpion Venoms / Q000037:antagonists & inhibitors / Q000276:immunology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D000939:Epitopes; D007128:Immunoglobulin Fragments; D009498:Neurotoxins; D012604:Scorpion Venoms; C055966:immunoglobulin Fv; C043052:variant-2 scorpion toxin