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Röllen K, Granzin J, Remeeva A, Davari MD, Gensch T, Nazarenko VV, Kovalev K, Bogorodskiy A, Borshchevskiy V, Hemmer S, Schwaneberg U, Gordeliy V, Jaeger KE, Batra-Safferling R, Gushchin I, Krauss U. The molecular basis of spectral tuning in blue- and red-shifted flavin-binding fluorescent proteins. J Biol Chem 2021; 296:100662. [PMID: 33862085 PMCID: PMC8131319 DOI: 10.1016/j.jbc.2021.100662] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 01/09/2023] Open
Abstract
Photoactive biological systems modify the optical properties of their chromophores, known as spectral tuning. Determining the molecular origin of spectral tuning is instrumental for understanding the function and developing applications of these biomolecules. Spectral tuning in flavin-binding fluorescent proteins (FbFPs), an emerging class of fluorescent reporters, is limited by their dependency on protein-bound flavins, whose structure and hence electronic properties cannot be altered by mutation. A blue-shifted variant of the plant-derived improved light, oxygen, voltage FbFP has been created by introducing a lysine within the flavin-binding pocket, but the molecular basis of this shift remains unconfirmed. We here structurally characterize the blue-shifted improved light, oxygen, voltage variant and construct a new blue-shifted CagFbFP protein by introducing an analogous mutation. X-ray structures of both proteins reveal displacement of the lysine away from the chromophore and opening up of the structure as instrumental for the blue shift. Site saturation mutagenesis and high-throughput screening yielded a red-shifted variant, and structural analysis revealed that the lysine side chain of the blue-shifted variant is stabilized close to the flavin by a secondary mutation, accounting for the red shift. Thus, a single additional mutation in a blue-shifted variant is sufficient to generate a red-shifted FbFP. Using spectroscopy, X-ray crystallography, and quantum mechanics molecular mechanics calculations, we provide a firm structural and functional understanding of spectral tuning in FbFPs. We also show that the identified blue- and red-shifted variants allow for two-color microscopy based on spectral separation. In summary, the generated blue- and red-shifted variants represent promising new tools for application in life sciences.
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Affiliation(s)
- Katrin Röllen
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Joachim Granzin
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich GmbH, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - Alina Remeeva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Mehdi D Davari
- Institute of Biotechnology, RWTH Aachen University, Aachen, Germany
| | - Thomas Gensch
- IBI-1: Molecular and Cellular Physiology, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Vera V Nazarenko
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Kirill Kovalev
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich GmbH, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany; Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia; Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France; Institute of Crystallography, RWTH Aachen University, Aachen, Germany
| | - Andrey Bogorodskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Valentin Borshchevskiy
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich GmbH, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany; Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Stefanie Hemmer
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Jülich, Germany; IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Ulrich Schwaneberg
- Institute of Biotechnology, RWTH Aachen University, Aachen, Germany; DWI-Leibniz Institute for Interactive Materials, Aachen, Germany
| | - Valentin Gordeliy
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich GmbH, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany; Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia; Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France
| | - Karl-Erich Jaeger
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Jülich, Germany; IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Renu Batra-Safferling
- IBI-7: Structural Biochemistry, Forschungszentrum Jülich GmbH, Jülich, Germany; JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - Ivan Gushchin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
| | - Ulrich Krauss
- Institut für Molekulare Enzymtechnologie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich GmbH, Jülich, Germany; IBG-1: Biotechnology, Forschungszentrum Jülich GmbH, Jülich, Germany.
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