Structural Determination of an Elastin-Mimetic Model Peptide, (Val-Pro-Gly-Val-Gly)₆, Studied by ¹³C CP/MAS NMR Chemical Shifts, Two-Dimensional off Magic Angle Spinning Spin-Diffusion NMR, Rotational Echo Double Resonance, and Statistical Distribution of Torsion Angles from Protein Data Bank

Abstract

The structure of an elastin-mimetic model peptide, (VPGVG) 6, was proposed by combining data obtained from quantitative use of the conformation-dependent 13 C NMR chemical shifts, twodimensional off magic angle spinning spin-diffusion solid-state NMR with 13 C double labeling of the peptides, rotational-echo double-resonance of 13 C, 15 N double labeling peptides, and statistical distribution of the backbone torsion angles of Val-Pro, Pro-Gly, and Gly-Val-Gly sequences from PDB. In essence, this approach drew upon several sets of data to formulate the resulting model, namely, that there is a distribution of conformations in this polypeptide. The Val-16 residue adopts torsion angles (φ, ψ) ) (-90 ( 15°, 120 ( 15°). In contrast, bimodal distributions for the central residues of the (VPGVG) subunit were detected. For Pro-12, (φ, ψ) ) (-60 ( 15°, 120 ( 15°), 80%, and (φ, ψ) ) (-60 ( 15°, -30 ( 15°), 20%; for Gly-13, (φ, ψ) ) (90 ( 30°, -15 ( 30°) and (φ, ψ) ) (-90 ( 15°, 0 ( 15°), 60%, and (φ, ψ) ) (-105 ( 75°, 150 ( 30°), (φ, ψ) ) (120 ( 60°, 150 ( 30°), (φ, ψ) ) (-120 ( 60°, -150 ( 30°) and (φ, ψ) ) (120 ( 60°, -150 ( 30°), 40%. For Val-14, (φ, ψ) ) (-110 ( 20°, 130 ( 20°), 70%, and (φ, ψ) ) (-75 ( 15°, -15 ( 15°) 30%. To reconcile the torsion angles corresponding to the main component in the conformational distributions, a type-II β-turn structure was assigned to about 40% of the Pro-Gly pair.

Cooperativity between the Hydrophobic and Cross-linking Domains of Elastin

“…Current consensus indicates that a distribution of conformations (23,24), or "conformational ensemble" (32), is perhaps most likely and is also supported by this data. Others have shown that line widths of ϳ2 ppm or less are indicative of ordered structures (33).…”

“…Others have shown that line widths of ϳ2 ppm or less are indicative of ordered structures (33). Generally speaking, solid-state NMR studies of dehydrated elastin and elastin peptides have broader line shapes and, hence, are considered to be fairly disordered (20,24,32,34). EP20-24-24 and EP20-24-24[23U] are no exception.…”

Conformational Dynamics of Minimal Elastin‐Like Polypeptides: The Role of Proline Revealed by Molecular Dynamics and Nuclear Magnetic Resonance

“…Additionally, only a very small amount of other internal HBs are formed as a result of the temperature increase, and these only with a very low probability. The two most populated internal HBs at all temperatures in the trans simulations are formed between the carbonyl oxygen of V (4) and the amide proton of either V (7) or G (8) , whereby the V (4) ···V (7) HB is populated to a slightly larger extent. This internal HB can be formed in many b-type turns in which the proline residue occurs in the trans conformation, thus allowing the peptide to double back on itself.…”

“…[37] Moreover, it emerged from these studies that the polyA C H T U N G T R E N N U N G (VPGVG) repeat is essential to the mechanical and elastic properties of elastins, which makes this unit ideal for use as a model system to investigate the elusive relationship between the structure and function of elastin. [5,7] For this reason, elastin-derived biopolymers, represented by (VPGVG) n , have attracted much attention due to their potential uses as biomaterials and for other industrial applications. [9,10] The way in which elastin is able to expand reversibly under mechanical strain is the source of much controversy, embodying concepts such as classical rubber elasticity, [11] librational entropy mechanisms, [6] and hydrophobic collapse.…”

Local conformation of serine residues in a silk model peptide, (Ala–Gly–Ser–Gly–Ala–Gly)5, studied with solid-state NMR:REDOR

“…The ratio of two components, antiparallel b-sheet and random coil, at each Ser residue in (AGS-GAG) 5 was obtained by comparison of the observed REDOR plots with calculated ones. 11 The results reveal that the conformational distribution is different among Ser residues and is within 20-40%, depending on the position of the repeated sequence, Ala-Gly-Ser-Gly-Ala-Gly.…”