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 H–NC^α–H and H–C^αC^β–H 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 C^α–C^β 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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