Buyan Pan is one of the winners of the Peptide Science Poster Awards at the 2019 American Peptide Symposium in Monterey, CA. She is a Ph.D. candidate currently working jointly in the labs of E. James Petersson and Elizabeth Rhoades at the University of Pennsylvania. She and her colleagues have recently published a paper in ACS Chemical Biology titled Chemoenzymatic Semisynthesis of Phosphorylated α-Synuclein Enables Identification of a Bidirectional Effect on Fibril Formation.
Post-translational modifications (PTMs) impact the pathological aggregation of α-synuclein (αS), a hallmark of Parkinson’s disease (PD). In this report they synthesize αS phosphorylated at tyrosine 39 (pY39) through a novel route using in vitro enzymatic phosphorylation of a fragment followed by ligation to form the full-length protein.
They can execute this synthesis in combination with unnatural amino acid mutagenesis to include two fluorescent labels for Förster resonance energy transfer (FRET) studies. They also determine the effect of pY39 on the aggregation of αS and compare our authentically phosphorylated material to the corresponding glutamate 39 “phosphomimetic.”
They find that αS-pY39 can either accelerate or decelerate aggregation, depending on the fraction of phosphorylated protein. The αS-E39 mutant can qualitatively reproduce some, but not all, of these effects. FRET measurements and analysis of existing structures of αS help to provide an explanation for this phenomenon. The results have important implications for the treatment of PD patients with tyrosine kinase inhibitors and highlight the importance of validating phosphomimetics through studies of authentic PTMs.
ACS Chem. Biol. 2020, 15, 3, 640-645