Spatial structure of insectotoxin I5A Buthus eupeus by 1H nuclear magnetic resonance spectroscopy

A.L. Lomize, V. N. Maiorov, A. S. Arseniev

M. M. Shemyakin Institute of Bioorganic Chemistry, Academy of Sciences of the USSR, Moscow

Abstract: The solution structure of insectotoxin I5A (35 residues) from scorpion Buthus enpeus was determined on the basis of 386 interproton distance restraints 12 hydrogen-bonding restraints and 113 dihedral angle restraints derived from 1H NMR experiments. A group of 20 structures was calculated with the distance geometry program DIANA followed by the restrained energy minimization with the program CHARMM. The atomic RMS distribution about the mean coordinate position is 0.640.11 Å for the backbone atoms and 1.350.20 Å for all atoms. The structure contains an α-helix (residues 1020) and a three stranded antiparallel β-sheet (residues 25, 2428 and 2933). A pairing of the eight cysteine residues of insectotoxin I5A was established basing on NMR data. Three disulfide bridges (residues 219, 1631 and 2033) connect the α-helix with the β-sheet, and the fourth one (526) joins -strands together. The spatial fold of secondary structure elements (the α-helix and the β-sheet) of the insectotoxin I5A is very similar to those of the other short and long scorpion toxins in spite of a low (about 20%) sequence homology.

Russian Journal of Bioorganic Chemistry 1991, 17 (12):1613-1632

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