Structure of an elastin-mimetic polypeptide by solid-state NMR chemical shift analysis

The conformation of an elastin-mimetic recombinant protein, [(VPGVG)(4)(VPGKG)](39), is investigated using solid-state NMR spectroscopy. The protein is extensively labeled with C-13 and N-15, and two-dimensional C-13-C-13 and N-15-C-13 correlation experiments were carried out to resolve and assign the isotropic chemical shifts of the various sites. The Pro N-15, (13)Calpha and (13)Cbeta isotropic shifts, and the Gly-3 Calpha isotropic and anisotropic chemical shifts support the predominance of type-II beta-turn structure at the Pro-Gly pair but reject a type-I beta-turn. The Val-1 preceding Pro adopts mostly beta-sheet torsion angles, while the Val-4 chemical shifts are intermediate between those of helix and sheet. The protein exhibits a significant conformational distribution, shown by the broad line widths of the N-15 and C-13 spectra. The average chemical shifts of the solid protein are similar to the values in solution, suggesting that the low-hydration polypeptide maintains the same conformation as in solution. The ability to measure these conformational restraints by solid-state NMR opens the possibility of determining the detailed structure of this class of fibrous proteins through torsion angles and distances. (C) 2003 Wiley Periodicals, Inc.