Structure and conformational heterogeneity of the weak toxin from the cobra Naja kaouthia venom

摘要: Resonances in the two-dimensional 1H NMR spectra of a weak toxin (WTX) from venom cobra Naja kaouthiafor all 65 amino acid residues were assigned. The sequence WTX, determined by sequential assignment spin systems, was found to be similar that CM-9a N. kaouthiavenom. Unlike CM-9a, WTX contains an additional Trp36 residue; Lys50 and Tyr52 are interchanged; there is Thr residue place Arg2. For some presence two components approximately equal intensities shown, which explained conformational heterogeneity polypeptide owing cis–transisomerization peptide bond Arg32–Pro33. data (contacts nuclear Overhauser effect, constants spin–spin coupling protons, rates exchange amide protons for deuterium solvent) made it possible determine secondary structure forms characterized antiparallel β-sheets, one consists strands (regions 1–5 13–17) other, three 23–28, 38–43, 55–59).