Structural requirements essential for elastin coacervation: favorable spatial arrangements of valine ridges on the three‐dimensional structure of elastin‐derived polypeptide (VPGVG)n

Abstract

The elastin precursor tropoelastin possesses a number of polymeric peptides with repeating 3-9 mer sequences. One of these is the pentapeptide Val-Pro-Gly-Val-Gly (VPGVG) present in almost all animal species, and its polymer (VPGVG)n coacervates just as does tropoelastin. In the present study, in order to explore the structural requirements essential for coacervation, (VPGVG)n and its shortened repeat analogs (VPGV)n, (VPG)n, and (PGVG)n were synthesized and their structural properties were investigated. In our turbidity measurements, (VPGVG)n demonstrated complete reversible coacervation in agreement with previous findings. The Gly(5) -deleted polymer (VPGV)n also achieved self-association, though the onset of self-association occurred at a lower temperature. However, the dissociation of (VPGV)n upon temperature lowering was found to occur in a three-step process; the Val(i) (4) -Val(i+1) (1) structure arising in the VPGV polypeptide appeared to perturb the dissociation. No self-association was observed for (VPG)n or (PGVG)n repeats. Spectroscopic measurements by CD, FT-IR, and (1) H-NMR showed that the (VPGV)n and (VPG)n both assumed ordered structures similar to that of (VPGVG)n. These results demonstrated that VPGVG is a structural element essential to achieving the β-spiral structure required for self-association followed by coacervation, probably due to the ideal spatial arrangement of the hydrophobic Val residues.

Development of short and highly potent self‐assembling elastin‐derived pentapeptide repeats containing aromatic amino acid residues

“…When the solution temperature was lowered again, the turbidity began to decrease at around 8°C, returning to its original value at 4°C. The turbidity intensity of the peptide (WPGVG) 3 , which only consisted of 15 amino acids, was almost the same as that of the elastin‐derived polypentapeptide (VPGVG) n ( n > 40), which comprised at least 200 amino acid residues as previously described . In contrast, the peptides (WPGVG) n ( n = 1, 2) did not show turbidity changes in any temperature range at a concentration of 30 mg/ml.…”

High-molecular-weight poly(Gly-Val-Gly-Val-Pro) synthesis through microwave irradiation

“…Also, this phenomenon was observed when the molecular weight of poly(VPGVG) exceeded approximately 17 000, and it was assumed to contain more than 40 repeating units of VPGVG. Further, as mentioned in the preceding texts, it distinctly exhibited coacervation [32][33][34][35]. However, the synthesis required 2-4 weeks.…”

“…An H‐VPGVG‐ p ‐nitrophenyl ester (‐ONp) was synthesized and introduced as the monomer unit. The resulting compound, H‐VPGVG‐ONp, was polymerized in a concentrated dimethyl sulfoxide solution for 2–4 weeks at 25 °C . The synthesized poly(VPGVG) exhibited temperature sensitivity (LCST) and coacervation similar to those of the recombinant polypeptide obtained from Escherichia coli .…”

Protein‐based functional nanomaterial design for bioengineering applications

“…Additionally, it also helps explain the thermo‐responsiveness of elastin that depends on the changes in the entropy of water molecules resulting from the changes in water/elastin hydrogen‐bonding stability as the temperature increases. The theory can also be used to explain the increases in the proportions of ordered structures as seen in Fourier transform infrared (FTIR) and circular dichroism spectra resulting from elastin dehydration during its ITT that likely concentrates β‐turns as the protein coacervates …”