title: A Dynamic Model of pH-Induced Protein G'e Higher Order Structure Changes derived from Mass Spectrometric Analyses.
abstract: To obtain insight into pH change-driven molecular dynamics, we studied the higher order structure changes of protein G'e at the molecular and amino acid residue levels in solution by using nanoESI- and IM-mass spectrometry, CD spectroscopy, and protein chemical modification reactions (protein footprinting). We found a dramatic change of the overall tertiary structure of protein G'e when the pH was changed from neutral to acidic, whereas its secondary structure features remained nearly invariable. Limited proteolysis and surface-topology mapping of protein G'e by fast photochemical oxidation of proteins (FPOP) under neutral and acidic conditions reveal areas where higher order conformational changes occur on the amino-acid residue level. Under neutral solution conditions, lower oxidation occurs for residues of the first linker region, whereas greater oxidative modifications occur for amino-acid residues of the IgG-binding domains I and II. We propose a dynamic model of pH-induced structural changes in which protein G'e at neutral pH adopts an overall tight conformation with all four domains packed in a firm assembly, whereas at acidic pH, the three IgG-binding domains form an elongated alignment, and the N-terminal, His-tag-carrying domain unfolds. At the same time the individual IgG-binding domains themselves seem to adopt a more compacted fold. As the secondary structure features are nearly unchanged at either pH, interchange between both conformations is highly reversible, explaining the high reconditioning power of protein G'e-based affinity chromatography columns.
authors.affiliation: Proteome Center Rostock, University Medicine Rostock , Schillingallee 69, 18059 Rostock, Germany.
authors.forename: Yelena
authors.initials: Y
authors.lastname: Yefremova
authors.affiliation: Proteome Center Rostock, University Medicine Rostock , Schillingallee 69, 18059 Rostock, Germany.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Al-Majdoub
authors.affiliation: Proteome Center Rostock, University Medicine Rostock , Schillingallee 69, 18059 Rostock, Germany.
authors.forename: Kwabena F M
authors.initials: KF
authors.lastname: Opuni
authors.affiliation: Proteome Center Rostock, University Medicine Rostock , Schillingallee 69, 18059 Rostock, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Koy
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Yuetian
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Chemistry, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Gross
authors.affiliation: Proteome Center Rostock, University Medicine Rostock , Schillingallee 69, 18059 Rostock, Germany.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Glocker
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D014357:Trypsin / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D014357:Trypsin