The local structure of a protein insectotoxin I5A from Buthus eupeus determined from 1H NMR data

A. L. Lomize, A. S. Arseniev, I. V. Maslennikov, V. F. Bystrov

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

Abstract: The local structure (torsion angles φ, ψ) and χ1 of amino acid residues) of insectotoxin I5A (35 residues) of scorpion Buthus eupeus has been determined from cross-peak integral intensities in two-dimensional nuclear Overhauser enhancement (NOESY) spectra and spin coupling constants of vicinal HNCαH and HCαCβH protons. The local structure determination was carried out by fitting complete relaxation matrix of peptide unit protons (protons of a given residue and NH: proton of the next residue in the amino acid sequence) with experimental NOESY cross-peak intensities. The obtained intervals of backbone torsional angles φ and ψ consistent with NMR data were determined for all but Gly residues. The predominant CαCβ rotamer of the side chain has been unambiguously determined for 42% of the insectotoxin1 amino acid residues whereas for another 46% residues experimental data are fitted equally well with two rotamers. Stereospecific assignments were obtained for 38% of β-methylene groups. The determined torsional angles φ, ψ and χ1 correspond to the sterically allowed conformations of the amino acid residues and agree with the insectotoxin secondary structure established earlier by 1H NMR spectros-copy.

Russian Journal of Bioorganic Chemistry 1990, 16 (10):1310-1324

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