Abstract: Molecular dynamics simulations were employed to study the
conformational dynamics and thermal stabilities of the large αβ-tubulin dimer systems under various conditions. The
αβ-tubulin dimer at ambient and cryogenic
temperatures remains stable around the native conformations, and the water
solvent molecules tend to stabilize the native conformations through the
formation of complex hydrogen-bonding networks. The elevation of temperature
severely destroys the native conformations and the bioactivities, especially in
aqueous solution. It was caused by the lack of intra- and inter-molecular
interactions and the decrease of water polarity at higher temperatures. The
conformational analysis of the selected segment (β15-QIGAKFWEVIS) provides detailed information on the whole proteins.
It was revealed that the local structures of proteins at ambient and cryogenic
temperatures have obvious differences albeit the overall structures are close
to each other. The selected segments under high temperatures are dominated by
random coils instead of native helix at ambient and cryogenic temperatures,
accompanied by more diversities and faster conversions of conformations. In
addition, the temperature or/and the solvent are capable of altering the
secondary structures and further the conformations of the segments and the
whole proteins. At ambient temperatures, the water solvent helps the proteins
to achieve the native conformation with bioactivities. Different from the
corresponding segments in proteins, the truncated peptides are endowed with
higher structural flexibilities and characterized by random coils even at
ambient temperatures, along with the disappearance of helical hydrogen bonds.
Keywords: Protein structures, stability, solvent effects, tubulin segments, molecular dynamics
