title: Structure of a PEGylated protein reveals a highly porous double-helical assembly.
abstract: PEGylated proteins are a mainstay of the biopharmaceutical industry. Although the use of poly(ethylene glycol) (PEG) to increase particle size, stability and solubility is well-established, questions remain as to the structure of PEG-protein conjugates. Here we report the structural characterization of a model β-sheet protein (plastocyanin, 11.5 kDa) modified with a single PEG 5,000. An NMR spectroscopy study of the PEGylated conjugate indicated that the protein and PEG behaved as independent domains. A crystal structure revealed an extraordinary double-helical assembly of the conjugate, with the helices arranged orthogonally to yield a highly porous architecture. Electron density was not observed for the PEG chain, which indicates that it was disordered. The volume available per PEG chain in the crystal was within 10% of the calculated random coil volume. Together, these data support a minimal interaction between the protein and the synthetic polymer. Our work provides new possibilities for understanding this important class of protein-polymer hybrids and suggests a novel approach to engineering protein assemblies.
authors.affiliation: School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland.
authors.forename: Giada
authors.initials: G
authors.lastname: Cattani
authors.affiliation: School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Lutz
authors.initials: L
authors.lastname: Vogeley
authors.affiliation: School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Crowley
mesh_terms: D019906:Nuclear Magnetic Resonance, Biomolecular; D011092:Polyethylene Glycols / Q000737:chemistry*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins; D011092:Polyethylene Glycols