A β-Hairpin Structure in a 13-mer Peptide That Binds α-Bungarotoxin with High Affinity and Neutralizes Its Toxicity

• Published in: Proceedings of the National Academy of Sciences - PNAS 2001-06, Vol.98 (12), p.6629-6634
• Main Authors: Scherf, Tali, Kasher, Roni, Balass, Moshe, Fridkin, Mati, Fuchs, Sara, Katchalski-Katzir, Ephraim
• Format: Article
• Language: English
• Subjects: a-Bungarotoxin; Amino acids; Atomic interactions; Atoms; Biochemistry; Biological Sciences; Biology; Bungarotoxins - chemistry; Bungarotoxins - metabolism; Bungarotoxins - toxicity; Bungarus; Magnetic Resonance Spectroscopy; Molecular interactions; NMR; Nuclear magnetic resonance; Oligopeptides - chemistry; Oligopeptides - metabolism; Peptides; Physics; Poisons; Protein isoforms; Protein Structure, Secondary; Protons; Receptors; Receptors, Nicotinic - metabolism; Responsibility to protect; Structure-Activity Relationship; Toxins
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.111164298

Snake-venom α-bungarotoxin is a member of the α-neurotoxin family that binds with very high affinity to the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction. The structure of the complex between α-bungarotoxin and a 13-mer peptide (WRYYES-SLEPYPD) that binds the toxin with high affinity, thus inhibiting its interactions with AChR with an IC50of 2 nM, has been solved by1H-NMR spectroscopy. The bound peptide folds into a β-hairpin structure created by two antiparallel β-strands, which combine with the already existing triple-stranded β-sheet of the toxin to form a five-stranded intermolecular, antiparallel β-sheet. Peptide residues Y3P, E5P, and L8Phave the highest intermolecular contact area, indicating their importance in the binding of α-bungarotoxin; W1P, R2P, and Y4Palso contribute significantly to the binding. A large number of characteristic hydrogen bonds and electrostatic and hydrophobic interactions are observed in the complex. The high-affinity peptide exhibits inhibitory potency that is better than any known peptide derived from AChR, and is equal to that of the whole α-subunit of AChR. The high degree of sequence similarity between the peptide and various types of AChRs implies that the binding mode found within the complex might possibly mimic the receptor binding to the toxin. The design of the high-affinity peptide was based on our previous findings: (i) the detection of a lead peptide (MRYYES-SLKSYPD) that binds α-bungarotoxin, using a phage-display peptide library, (ii) the information about the three-dimensional structure of α-bungarotoxin/lead-peptide complex, and (iii) the amino acid sequence analysis of different AChRs.