Periodic introduction of aromatic units in polypeptides via chemoenzymatic polymerization to yield specific secondary structures with high thermal stability

Abstract

Polypeptides containing periodic aromatic residues in their main chains were synthesized via papain-catalyzed chemoenzymatic polymerization of tripeptide ester monomers under moderate conditions in aqueous buffers. As the monomer, 4-aminobenzoic acid (Abz) was modified with Gly or Ala at the N-and C-termini to mitigate the poor substrate specificity of papain to unnatural amino acids. The tripeptide esters, namely, GlyAbzGly and AlaAbzAla ethyl esters, can be recognized and polymerized by papain, resulting in the polypeptides poly(GlyAbzGly) and poly(AlaAbzAla), respectively, with periodic sequences containing Abz units every three residues. Copolymerization of tripeptide esters with Gly or Ala ethyl ester also proceeded in the presence of papain. The secondary structures of the Abz-containing polypeptides were investigated by IR and wide-angle X-ray diffraction (WAXD) analysis. The WAXD profile of poly(GlyAbzGly) was similar to that of polyGly, whereas poly(AlaAbzAla) adopted a sheet-like structure similar to the β-sheet of polyAla. Thermal analysis of Abz-containing polypeptides revealed that the high thermal stability of the Abz-containing polypeptides is related to the distinct sequences that periodically include Abz residues.

Peptide-Based Polyion Complex Vesicles That Deliver Enzymes into Intact Plants To Provide Antibiotic Resistance without Genetic Modification

“…To polymerize N ε -Boc-protected l -lysine methyl ester, we used chemoenzymatic polymerization according to the previous literature. , A solution of N ε -Boc-protected l -lysine methyl ester hydrochloride (5 g, 16.8 mmol) in phosphate buffer (8.4 mL, 1.0 M, pH = 8.0) was placed in a glass tube equipped with a stirring bar. To this was added a solution of papain (0.84 g) in phosphate buffer (5.6 mL) in one portion.…”

Self-assembly and hydrogel formation ability of Fmoc-dipeptides comprising α-methyl-L-phenylalanine

“…Supramolecular nanostructures, which consist of selfassembling peptide derivatives, have attracted rapidly increasing attention for the fabrication of various biofunctional materials [1][2][3][4][5][6][7][8][9]. Recent seminal works have revealed that short peptides bearing an aromatic group at their N-termini have a robust potential to self-assemble into supramolecular nanostructures under aqueous conditions with subsequent hydrogel formation, facilitating active exploration [10][11][12][13][14][15][16][17].…”

From structural to functional materials: a green way to produce functional biopolymers based on polypeptides

“…However, unnatural amino acid monomers are tightly excluded during the enzymatic reaction� Our initial attempt to polymerize unnatural amino acid esters in the presence of various proteases was not satisfactory: the amount of unnatural amino acids that can be incorporated into polypeptide sequences is quite limited, 12 which motivated us to design unnatural amino acid-containing oligopeptide ester monomers� Sandwiching the unnatural amino acids amid natural amino acids allows proteases to recognize such species in the substrate pocket, leading to successful polymerization of these oligopeptide monomers (Figure 4). [13][14][15] A typical unnatural amino acid, 2-aminoisobutyric acid (Aib), is an α,α-disubstituted amino acid with bulky side groups. Introduction of Aib residues in polypeptides is known to strongly induce a helical conformation due to the bulky structure� We prepared a tripeptide ethyl ester with an alanine-Aib-alanine (AlaAibAla) sequence for the monomer for chemoenzymatic polym-erization� 15 Neither nor a Aib-containing dipeptide monomer was found to be able to polymerize in the presence of papain because the Aib unit has a poor affinity for papain.…”