[Study of long-chain neurotoxins from Naja naja siamensis and Naja naja oxiana venoms by circular dichroism and fluorescence]. / Issledovanie neirotoksinov dlinnogo tipa iz iada Naja naja siamensis i Naja naja oxiana metodami krugovogo dikhroizma i fluorestsentsii.

ABSTRACT

CD and fluorescence spectroscopy were used to study the conformational mobility of long-chain neurotoxins from the venom of cobra Naja naja siamensis and Naja naja oxiana (STX and NT-I, respectively). Microenvironment of tryptophan residues in these neurotoxins and their lysine-modified derivatives was also analyzed. Ionization of His22 (pK 5,4-5,6) in STX influences the invariant Trp29 microenvironment. No conformational change was observed on titration of single His residue situated in the C-terminal part of NT-I. Attachment of dansyl groups at Lys39 or Lys60 residues in NT-I is without effect on the native neurotoxin conformation. The distances from these labels to Trp29 or Trp33 indole rings are no shorter than 1,0 nm. The data obtained for STX and NT-I indicate that the STX X-ray structure may serve as a basis for studies on the solution conformation of the long-chain neurotoxins.