Total chemical synthesis of fully functional Photoactive Yellow Protein

The Photoactive Yellow Protein (PYP) is a structural prototype for the PAS superfamily of proteins, which includes hundreds of receptor and regulatory proteins from all three kingdoms of life. PYP itself is a small globular protein that undergoes a photocycle involving a series of conformational changes in response to light excitation of its p-coumaric acid chromophore, making it an excellent model system to study the molecular basis of signaling in the PAS super family. To enable novel chemical approaches to elucidating the structural changes that accompany signaling in PYP, we have chemically synthesized the 125 amino acid residue protein molecule using a combination of Boc chemistry solid phase peptide synthesis and native chemical ligation. Synthetic PYP exhibits the wildtype photocycle, as determined in photobleaching studies. Planned future studies include incorporation of site-specific isotopic labels into specific secondary structural elements to determine which structural elements are involved in signaling state formation using difference FTIR spectroscopy.