Molecular dynamics of two homologous neurotoxins revealed by 1H- 2H exchange An infrared spectrometry study

Abstract

Temperature effects on the hydrogen exchange kinetics and the infrared spectra of two homologous snake neurotoxins ( Laticauda semifasciata erabutoxin b and Naja nigricollis toxin α) were investigated between 10 and 40°C, at their isoionic pH. (1) Erabutoxin b is more accessible to the solvent than toxin α. (2) With increasing temperature, both toxin molecules undergo a global transition affecting the most accessible as well as the most buried hydrogens: the overall accessibility changes are more important for erabutoxin b than for toxin α. The different conformational stabilities of the toxins are also qualitatively supported by the temperature-induced shifts which affect the infrared amide I band of toxin α only. The existence of two conformer families could be responsible for the different conformational stability of these proteins.