Solution conformation of an antibacterial peptide, sarcotoxin IA, as determined by 1H‐NMR

Abstract

The solution conformation of sarcotoxin IA, which is an antibacterial peptide isolated from Sarcophaga peregrina with a molecular mass of 4 kDa, was determined by NMR spectroscopy and hybrid distance geometry/dynamical simulated annealing calculations. On the basis of 227 experimental constraints, including 185 distance constraints obtained from NOE and 42 constraints associated with 21 hydrogen bonds, a total of 18 converged structures of sarcotoxin IA were obtained. The final 18 converged structures exhibit backbone‐atomic root‐mean‐square differences about the averaged coordinate positions of 0.070±0.027 nm for residues 3–23 and 0.040±0.017 nm for residues 28–38. It has been indicated that sarcotoxin IA consists of two amphiphilic α‐helical regions, i.e. helix I (Leu3–Gln23) and helix II (Ala28–Ala38), with a hinge region (Gly24–Ile27), which connects helix I and helix II. We conclude that these two amphiphilic helical segments of sarcotoxin IA are of importance for the expression of the antibacterial activity. Copyright © 1993, Wiley Blackwell. All rights reserved