Conformation of thymosin β4 in water determined by NMR spectroscopy

Abstract

The conformational preferences of a 43‐amino‐acid G‐actin‐binding peptide, thymosin β4, in water at 1, 4 and 14°C, and at pH 3.0 and 6.5 were studied by NMR. NMR showed that thymosin β4 lacks a uniquely folded conformation in water. However, some preferential α‐helical conformations of thymosin β4 can be observed in aqueous solutions. The segment at residues 5–16 showed characteristic interactions for conformations in both the β‐strand and α‐helical regions of the ø‐Ψ space, based on strong CαH(i)‐NH(i+1) interactions and NH‐NH, CαH(i)‐NH(i+3), and CαH(i)‐CβH(i+3) interactions, respectively. At 1–4°C, another segment at residues 31–37 also shows both β and α conformations, forming however a less well‐defined helix than the segment at residues 5–16. At 14°C, the conformational population of the helix at positions 5–16 is shifted more towards the random and turn‐like structures, whereas the segment at positions 31–37 becomes exclusively a random coil. Copyright © 1993, Wiley Blackwell. All rights reserved