Analytical gel filtration experiments to determine the MvaI oligomeric state and the stoichiometry of DNA binding for the oligoduplex 1 shown in ()

<p><b>Copyright information:</b></p><p>Taken from "Restriction endonuclease MvaI is a monomer that recognizes its target sequence asymmetrically"</p><p></p><p>Nucleic Acids Research 2007;35(6):2035-2046.</p><p>Published online 7 Mar 2007</p><p>PMCID:PMC1874612.</p><p>© 2007 The Author(s)</p> Elution profiles were recorded simultaneously at 260 and 280 nm and deconvoluted to obtain separate curves for the MvaI (blue) and DNA (red) concentration. () MvaI alone, () DNA alone, () mixture with a 2:1 molar excess of MvaI over DNA, () stoichiometric mixture, () mixture with a 2:1 molar excess of DNA over MvaI, () calibration curve for Superose ™ 12 HR 10/30 column (Amersham Biosciences) with standards from Biorad (vitamin B-12, 1.35 kDa; myoglobin, 17 kDa; ovalbumin, 44kDa; IgG, 150 kDa and thyroglobin, 670 kDa)

Structural Basis for Efficient Chromophore Communication and Energy Transfer in a Constructed Didomain Protein Scaffold

The construction of useful functional biomolecular components not currently part of the natural repertoire is central to synthetic biology. A new light-capturing ultra-high-efficiency energy transfer protein scaffold has been constructed by coupling the chromophore centers of two normally unrelated proteins: the autofluorescent protein enhanced green fluorescent protein (EGFP) and the heme-binding electron transfer protein cytochrome <i>b</i>₅₆₂ (cyt <i>b</i>₅₆₂). Using a combinatorial domain insertion strategy, a variant was isolated in which resonance energy transfer from the donor EGFP to the acceptor cyt <i>b</i>₅₆₂ was close to 100% as evident by virtually full fluorescence quenching on heme binding. The fluorescence signal of the variant was also sensitive to the reactive oxygen species H₂O₂, with high signal gain observed due to the release of heme. The structure of oxidized holoprotein, determined to 2.75 Å resolution, revealed that the two domains were arranged side-by-side in a V-shape conformation, generating an interchromophore distance of ∼17 Å (14 Å edge-to-edge). Critical to domain arrangement is the formation of a molecular pivot point between the two domains as a result of different linker sequence lengths at each domain junction and formation of a predominantly polar interdomain interaction surface. The retrospective structural analysis has provided an explanation for the basis of the observed highly efficient energy transfer through chromophore arrangement in the directly evolved protein scaffold and provides an insight into the molecular principles by which to design new proteins with coupled functions

Structural Basis for Efficient Chromophore Communication and Energy Transfer in a Constructed Didomain Protein Scaffold

The construction of useful functional biomolecular components not currently part of the natural repertoire is central to synthetic biology. A new light-capturing ultra-high-efficiency energy transfer protein scaffold has been constructed by coupling the chromophore centers of two normally unrelated proteins: the autofluorescent protein enhanced green fluorescent protein (EGFP) and the heme-binding electron transfer protein cytochrome <i>b</i>₅₆₂ (cyt <i>b</i>₅₆₂). Using a combinatorial domain insertion strategy, a variant was isolated in which resonance energy transfer from the donor EGFP to the acceptor cyt <i>b</i>₅₆₂ was close to 100% as evident by virtually full fluorescence quenching on heme binding. The fluorescence signal of the variant was also sensitive to the reactive oxygen species H₂O₂, with high signal gain observed due to the release of heme. The structure of oxidized holoprotein, determined to 2.75 Å resolution, revealed that the two domains were arranged side-by-side in a V-shape conformation, generating an interchromophore distance of ∼17 Å (14 Å edge-to-edge). Critical to domain arrangement is the formation of a molecular pivot point between the two domains as a result of different linker sequence lengths at each domain junction and formation of a predominantly polar interdomain interaction surface. The retrospective structural analysis has provided an explanation for the basis of the observed highly efficient energy transfer through chromophore arrangement in the directly evolved protein scaffold and provides an insight into the molecular principles by which to design new proteins with coupled functions