The solution conformation of the synthetic tubulin fragment Ac-tubulin-α(430–441)-amide based on two-dimensional ROESY experiments

Abstract

Ac-tubulin-α(430–441)-amide, a synthetic fragment of tubulin, has been studied by 300-MHz 1H nuclear magnetic resonance spectroscopy in 80% CD3OH/20% D2O solution at neutral pH. The results, based on two-dimensional phase-sensitive techniques such as COSY, RELAY, and ROESY, reveal that the dodecapeptide exists in a non-random conformation. The conformation can be described as an α helix for the N-terminal five residues, followed by an extended section. The extended part exhibits a significant change in the nuclear Overhauser enhancement (nOe) pattern between units number 9 and 10. Together with long-range nOe data this can be attributed to a folding back that allows the close proximity of the C-terminal half of the extended chain and amino acids 3 to 5 of the α-helical turn. The existence of an α helix is in good agreement with previously published circular dichroism data.