Structural stabilization of botulinum neurotoxins by tyrosine phosphorylation

FEBS Lett. 1998 Jun 5;429(1):78-82. doi: 10.1016/s0014-5793(98)00571-7.


Tyrosine phosphorylation of botulinum neurotoxins augments their proteolytic activity and thermal stability, suggesting a substantial modification of the global protein conformation. We used Fourier-transform infrared (FTIR) spectroscopy to study changes of secondary structure and thermostability of tyrosine phosphorylated botulinum neurotoxins A (BoNT A) and E (BoNT E). Changes in the conformationally-sensitive amide I band upon phosphorylation indicated an increase of the alpha-helical content with a concomitant decrease of less ordered structures such as turns and random coils, and without changes in beta-sheet content. These changes in secondary structure were accompanied by an increase in the residual amide II absorbance band remaining upon H-D exchange, consistent with a tighter packing of the phosphorylated proteins. FTIR and differential scanning calorimetry (DSC) analyses of the denaturation process show that phosphorylated neurotoxins denature at temperatures higher than those required by non-phosphorylated species. These findings indicate that tyrosine phosphorylation induced a transition to higher order and that the more compact structure presumably imparts to the phosphorylated neurotoxins the higher catalytic activity and thermostability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Botulinum Toxins / chemistry*
  • Calorimetry, Differential Scanning
  • Phosphorylation
  • Protein Folding
  • Protein Structure, Secondary
  • Tyrosine / chemistry*


  • Tyrosine
  • Botulinum Toxins