title: De novo design, synthesis, and characterization of quinoproteins.
abstract: Quinones and quinoproteins are essential redox components and enzymes in biological systems. Here, we report the de novo design, synthesis, and properties of model four-alpha-helix bundle quinoproteins. The proteins were designed and constructed from three different helices with 21 or 22 amino acid residues by chemoselective ligation to a cyclic decapeptide template. A free cysteine unit is placed at the hydrophobic core of the protein for binding of ubiquinone-0 and menaquinone-0 through a thioether bond. The quinoproteins with molecular weights of 11-12 kDa were characterized by electrospray ionization mass spectrometry, UV/Vis spectroscopy, size-exclusion chromatography, circular dichroism measurements, (1)H NMR spectroscopy, cyclic voltammetry, and redox-induced FTIR difference spectroscopy. The midpoint redox potentials at pH 8 in aqueous solution E(m,8) of thioether conjugates with N-acetyl cysteine methyl ester were 89 mV and -63 mV and with a synthetic protein 229 mV and 249 mV versus standard hydrogen electrode (SHE) for ubiquinone-0 and menaquinone-0, respectively. Detailed redox-induced FTIR difference spectroscopic studies of the model compounds and quinoproteins show the special resonance features for C=O bands at 1656-1660 and 1655-1665 cm(-1) due to the sulfur substitution to ubiquinone-0 and menaquinone-0, respectively. The construction of model quinoproteins represents a significant step toward more complex artificial redox systems.
authors.affiliation: Institut für Biologie II/Biochemie, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany. wenwu.li@biologie.uni-freiburg.de
authors.forename: Wen-Wu
authors.initials: WW
authors.lastname: Li
authors.forename: Petra
authors.initials: P
authors.lastname: Hellwig
authors.forename: Michaela
authors.initials: M
authors.lastname: Ritter
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Haehnel
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004563:Electrochemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry; D017433:Protein Structure, Secondary; D011506:Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D011809:Quinones / Q000138:chemical synthesis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D010456:Peptides, Cyclic; D011506:Proteins; D011809:Quinones