Papain-Catalyzed, Sequence-Dependent Polymerization Yields Polypeptides Containing Periodic Histidine Residues

Abstract

His-containing polypeptides, including polyHis, are attractive materials due to the unique characteristics of the imidazole ring of the His residue. In particular, His-containing polypeptides with repetitive sequences have a variety of distinctive features based on their periodic structure. In this study, chemoenzymatic polymerization of ethyl ester monomers with sequences His, GlyHis, HisGly, and GlyHisGly with hydrophobic side chains on the imidazole ring was performed using papain as a catalyst. Sequence dependence in chemoenzymatic polymerization was observed for GlyHis-and HisGly-based monomers: GlyHis-based monomers did not undergo polymerization, whereas polymerization of HisGly-based monomers afforded polypeptides with a degree of polymerization from 6 to 38 and from 5 to 31 and a number-average degree of polymerization of 16.4 and 12.4 for poly(HisGly) and poly[His(Bu)Gly], respectively. The difference in polymerizability of these dipeptide monomers was supported by a docking simulation between these monomers and papain, where the ester group of the HisGly-based monomer was closer to the catalytic center of papain than that of the GlyHis-based monomer. Infrared spectroscopy and synchrotron wide-angle X-ray diffraction measurements indicated that poly(HisGly) formed a β-sheet structure whose crystallinity was 41.6%, whereas the other tripeptide-based polypeptides were more amorphous showing 19.6− 30.7% of crystallinity. Poly(HisGly) exhibited the highest thermal stability among all of the polypeptides in the thermogravimetric analysis, reflecting the difference in the secondary structures.

Ampholytic Peptides Consisting of an Alternating Lysine/Glutamic Acid Sequence for the Simultaneous Formation of Polyion Complex Vesicles

“…In addition to the series of polypeptides with an equimolar Lys/Glu composition, polypeptides with sequences rich in Glu residues were observed by MALDI-TOF MS analysis (there were up to 4 Lys residues less in this sequence than in the completely alternating sequence). This result was probably due to the transamidation , or hydrolysis of the Lys-Glu peptide bond in both the LysGlu(OEt)-OEt monomer and the generated poly[LysGlu(OEt)]. The Lys-rich peptides were more water soluble, resulting in an enrichment of Glu-rich sequences in the low-yield precipitate.…”

“…On the other hand, peptides with periodic sequences, including alternating peptides, are more accessible than peptides with complex sequences via solution-phase peptide synthesis. We and other groups have developed a chemoenzymatic peptide synthesis method using repeated aminolysis reactions of amino acid ester monomers mediated by proteases. − This enzymatic synthesis of peptides is an environmentally benign process and offers synthetic benefits in terms of stereo- and regioselectivity . This method is applicable to the polymerization of oligopeptide ester monomers, resulting in the formation of peptides with various periodic sequences.…”

Cell Wall‐Denaturing Molecules for Plant Gene Modification

“…Dipeptide‐based poly(HisGly) was likely to form a β‐sheet structure, while tripeptide‐based poly[GlyHis(BuCO 2 Et)Gly] or poly[GlyHis(BuCO 2 Bzl)Gly] formed random structures in the solid‐state (Figure 6E, F). [35] Since the secondary structures of peptides are well known to determine all peptide traits, different peptide structures might result in distinctive interaction abilities with cellulose. Thus, the postzwitterionic modification of these peptides might allow the design of new ZIPs that have fine secondary structures.…”