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Yukhnovets O, Höfig H, Bustorff N, Katranidis A, Fitter J. Impact of Molecule Concentration, Diffusion Rates and Surface Passivation on Single-Molecule Fluorescence Studies in Solution. Biomolecules 2022; 12:biom12030468. [PMID: 35327660 PMCID: PMC8946791 DOI: 10.3390/biom12030468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/09/2022] [Accepted: 03/16/2022] [Indexed: 12/04/2022] Open
Abstract
For single-molecule studies in solution, very small concentrations of dye-labelled molecules are employed in order to achieve single-molecule sensitivity. In typical studies with confocal microscopes, often concentrations in the pico-molar regime are required. For various applications that make use of single-molecule Förster resonance energy transfer (smFRET) or two-color coincidence detection (TCCD), the molecule concentration must be set explicitly to targeted values and furthermore needs to be stable over a period of several hours. As a consequence, specific demands must be imposed on the surface passivation of the cover slides during the measurements. The aim of having only one molecule in the detection volume at the time is not only affected by the absolute molecule concentration, but also by the rate of diffusion. Therefore, we discuss approaches to control and to measure absolute molecule concentrations. Furthermore, we introduce an approach to calculate the probability of chance coincidence events and demonstrate that measurements with challenging smFRET samples require a strict limit of maximal sample concentrations in order to produce meaningful results.
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Affiliation(s)
- Olessya Yukhnovets
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
- Correspondence: (O.Y.); (J.F.)
| | - Henning Höfig
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
| | - Nuno Bustorff
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
| | - Alexandros Katranidis
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
| | - Jörg Fitter
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
- Correspondence: (O.Y.); (J.F.)
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Junker NO, Vaghefikia F, Albarghash A, Höfig H, Kempe D, Walter J, Otten J, Pohl M, Katranidis A, Wiegand S, Fitter J. Impact of Molecular Crowding on Translational Mobility and Conformational Properties of Biological Macromolecules. J Phys Chem B 2019; 123:4477-4486. [PMID: 31059260 DOI: 10.1021/acs.jpcb.9b01239] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Effects of molecular crowding on structural and dynamical properties of biological macromolecules do depend on the concentration of crowding agents but also on the molecular mass and the structural compactness of the crowder molecules. By employing fluorescence correlation spectroscopy (FCS), we investigated the translational mobility of several biological macromolecules ranging from 17 kDa to 2.7 MDa. Polyethylene glycol and Ficoll polymers of different molecular masses were used in buffer solutions to mimic a crowded environment. The reduction in translational mobility of the biological tracer molecules was analyzed as a function of crowder volume fractions and was generally more pronounced in PEG as compared to Ficoll solutions. For several crowding conditions, we observed a molecular sieving effect, in which the diffusion coefficient of larger tracer molecules is reduced to a larger extent than predicted by the Stokes-Einstein relation. By employing a FRET-based biosensor, we also showed that a multiprotein complex is significantly compacted in the presence of macromolecular crowders. Importantly, with respect to sensor in vivo applications, ligand concentration determining sensors would need a crowding specific calibration in order to deliver correct cytosolic ligand concentration.
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Affiliation(s)
- Niklas O Junker
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Farzaneh Vaghefikia
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Alyazan Albarghash
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Henning Höfig
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Daryan Kempe
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Julia Walter
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | | | | | | | - Simone Wiegand
- Physikalische Chemie , Universität zu Köln , 50923 Köln , Germany
| | - Jörg Fitter
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
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Houwman JA, van Mierlo CPM. Folding of proteins with a flavodoxin-like architecture. FEBS J 2017; 284:3145-3167. [PMID: 28380286 DOI: 10.1111/febs.14077] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/13/2017] [Accepted: 04/03/2017] [Indexed: 12/21/2022]
Abstract
The flavodoxin-like fold is a protein architecture that can be traced back to the universal ancestor of the three kingdoms of life. Many proteins share this α-β parallel topology and hence it is highly relevant to illuminate how they fold. Here, we review experiments and simulations concerning the folding of flavodoxins and CheY-like proteins, which share the flavodoxin-like fold. These polypeptides tend to temporarily misfold during unassisted folding to their functionally active forms. This susceptibility to frustration is caused by the more rapid formation of an α-helix compared to a β-sheet, particularly when a parallel β-sheet is involved. As a result, flavodoxin-like proteins form intermediates that are off-pathway to native protein and several of these species are molten globules (MGs). Experiments suggest that the off-pathway species are of helical nature and that flavodoxin-like proteins have a nonconserved transition state that determines the rate of productive folding. Folding of flavodoxin from Azotobacter vinelandii has been investigated extensively, enabling a schematic construction of its folding energy landscape. It is the only flavodoxin-like protein of which cotranslational folding has been probed. New insights that emphasize differences between in vivo and in vitro folding energy landscapes are emerging: the ribosome modulates MG formation in nascent apoflavodoxin and forces this polypeptide toward the native state.
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Affiliation(s)
- Joseline A Houwman
- Laboratory of Biochemistry, Wageningen University and Research, The Netherlands
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Houwman JA, André E, Westphal AH, van Berkel WJH, van Mierlo CPM. The Ribosome Restrains Molten Globule Formation in Stalled Nascent Flavodoxin. J Biol Chem 2016; 291:25911-25920. [PMID: 27784783 PMCID: PMC5207065 DOI: 10.1074/jbc.m116.756205] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 10/13/2016] [Indexed: 11/06/2022] Open
Abstract
Folding of proteins usually involves intermediates, of which an important type is the molten globule (MG). MGs are ensembles of interconverting conformers that contain (non-)native secondary structure and lack the tightly packed tertiary structure of natively folded globular proteins. Whereas MGs of various purified proteins have been probed to date, no data are available on their presence and/or effect during protein synthesis. To study whether MGs arise during translation, we use ribosome-nascent chain (RNC) complexes of the electron transfer protein flavodoxin. Full-length isolated flavodoxin, which contains a non-covalently bound flavin mononucleotide (FMN) as cofactor, acquires its native α/β parallel topology via a folding mechanism that contains an off-pathway intermediate with molten globular characteristics. Extensive population of this MG state occurs at physiological ionic strength for apoflavodoxin variant F44Y, in which a phenylalanine at position 44 is changed to a tyrosine. Here, we show for the first time that ascertaining the binding rate of FMN as a function of ionic strength can be used as a tool to determine the presence of the off-pathway MG on the ribosome. Application of this methodology to F44Y apoflavodoxin RNCs shows that at physiological ionic strength the ribosome influences formation of the off-pathway MG and forces the nascent chain toward the native state.
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Affiliation(s)
- Joseline A Houwman
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Estelle André
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Adrie H Westphal
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Willem J H van Berkel
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Carlo P M van Mierlo
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
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Koubek J, Chen YR, Cheng RP, Huang JJT. Nonorthogonal tRNA(cys)(Amber) for protein and nascent chain labeling. RNA (NEW YORK, N.Y.) 2015; 21:1672-82. [PMID: 26194135 PMCID: PMC4536326 DOI: 10.1261/rna.051805.115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/08/2015] [Indexed: 05/14/2023]
Abstract
In vitro-transcribed suppressor tRNAs are commonly used in site-specific fluorescence labeling for protein and ribosome-bound nascent chains (RNCs) studies. Here, we describe the production of nonorthogonal Bacillus subtilis tRNA(cys)(Amber) from Escherichia coli, a process that is superior to in vitro transcription in terms of yield, ease of manipulation, and tRNA stability. As cysteinyl-tRNA synthetase was previously shown to aminoacylate tRNA(cys)(Amber) with lower efficiency, multiple tRNA synthetase mutants were designed to optimize aminoacylation. Aminoacylated tRNA was conjugated to a fluorophore to produce BODIPY FL-cysteinyl-tRNA(cys)(Amber), which was used to generate ribosome-bound nascent chains of different lengths with the fluorophore incorporated at various predetermined sites. This tRNA tool may be beneficial in the site-specific labeling of full-length proteins as well as RNCs for biophysical and biological research.
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MESH Headings
- Amino Acyl-tRNA Synthetases/genetics
- Amino Acyl-tRNA Synthetases/metabolism
- Bacillus subtilis/genetics
- Cell-Free System
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Fluorescent Dyes/chemistry
- In Vitro Techniques
- Models, Molecular
- Protein Biosynthesis
- RNA Stability
- RNA, Bacterial/biosynthesis
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Transfer, Cys/biosynthesis
- RNA, Transfer, Cys/chemistry
- RNA, Transfer, Cys/genetics
- Transfer RNA Aminoacylation
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Affiliation(s)
- Jiří Koubek
- Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Nankang, Taipei 11529, Taiwan Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Yet-Ran Chen
- Agricultural Biotechnology Research Center, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Richard Ping Cheng
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
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Houwman JA, Westphal AH, van Berkel WJH, van Mierlo CPM. Stalled flavodoxin binds its cofactor while fully exposed outside the ribosome. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1317-24. [PMID: 26073784 DOI: 10.1016/j.bbapap.2015.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/26/2015] [Accepted: 06/10/2015] [Indexed: 01/10/2023]
Abstract
Correct folding of proteins is crucial for cellular homeostasis. More than thirty percent of proteins contain one or more cofactors, but the impact of these cofactors on co-translational folding remains largely unknown. Here, we address the binding of flavin mononucleotide (FMN) to nascent flavodoxin, by generating ribosome-arrested nascent chains that expose either the entire protein or C-terminally truncated segments thereof. The native α/β parallel fold of flavodoxin is among the most ancestral and widely distributed folds in nature and exploring its co-translational folding is thus highly relevant. In Escherichia coli (strain BL21(DE3) Δtig::kan) FMN turns out to be limiting for saturation of this flavoprotein on time-scales vastly exceeding those of flavodoxin synthesis. Because the ribosome affects protein folding, apoflavodoxin cannot bind FMN during its translation. As a result, binding of cofactor to released protein is the last step in production of this flavoprotein in the cell. We show that once apoflavodoxin is entirely synthesized and exposed outside the ribosome to which it is stalled by an artificial linker containing the SecM sequence, the protein is natively folded and capable of binding FMN.
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Affiliation(s)
- Joseline A Houwman
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, the Netherlands
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, the Netherlands
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, the Netherlands
| | - Carlo P M van Mierlo
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, the Netherlands.
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