title: Conformational and aggregation properties of a PEGylated alanine-rich polypeptide.
abstract: The conformational and aggregation behavior of PEG conjugates of an alanine-rich polypeptide (PEG-c17H6) were investigated and compared to that of the polypeptide equipped with a deca-histidine tag (17H6). These polypeptides serve as simple and stimuli-responsive models for the aggregation behavior of helix-rich proteins, as our previous studies have shown that the helical 17H6 self-associates at acidic pH and converts to β-sheet structures at elevated temperature under acidic conditions. In the work here, we show that PEG-c17H6 also adopts a helical structure at ambient/subambient temperatures, at both neutral and acidic pH. The thermal denaturation behavior of 17H6 and PEG-c17H6 is similar at neutral pH, where the alanine-rich domain has no self-association tendency. At acidic pH and elevated temperature, however, PEGylation slows β-sheet formation of c17H6, and reduces the apparent cooperativity of thermally induced unfolding. Transmission electron microscopy of PEG-c17H6 conjugates incubated at elevated temperatures showed fibrils with widths of ∼20-30 nm, wider than those observed for fibrils of 17H6. These results suggest that PEGylation reduces β-sheet aggregation in these polypeptides by interfering, only after unfolding of the native helical structure, with interprotein conformational changes needed to form β-sheet aggregates.
authors.affiliation: Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716, USA.
authors.forename: Ayben
authors.initials: A
authors.lastname: Top
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: Kristi L
authors.initials: KL
authors.lastname: Kiick
mesh_terms: D000409:Alanine / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001688:Biological Products / Q000138:chemical synthesis / Q000378:metabolism*; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D015202:Protein Engineering / Q000379:methods*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D001688:Biological Products; D010455:Peptides; D011092:Polyethylene Glycols; D000409:Alanine