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Synakewicz M, Eapen RS, Perez-Riba A, Rowling PJE, Bauer D, Weißl A, Fischer G, Hyvönen M, Rief M, Itzhaki LS, Stigler J. Unraveling the Mechanics of a Repeat-Protein Nanospring: From Folding of Individual Repeats to Fluctuations of the Superhelix. ACS NANO 2022. [PMID: 35258937 DOI: 10.1101/2021.03.27.437344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Tandem-repeat proteins comprise small secondary structure motifs that stack to form one-dimensional arrays with distinctive mechanical properties that are proposed to direct their cellular functions. Here, we use single-molecule optical tweezers to study the folding of consensus-designed tetratricopeptide repeats (CTPRs), superhelical arrays of short helix-turn-helix motifs. We find that CTPRs display a spring-like mechanical response in which individual repeats undergo rapid equilibrium fluctuations between partially folded and unfolded conformations. We rationalize the force response using Ising models and dissect the folding pathway of CTPRs under mechanical load, revealing how the repeat arrays form from the center toward both termini simultaneously. Most strikingly, we also directly observe the protein's superhelical tertiary structure in the force signal. Using protein engineering, crystallography, and single-molecule experiments, we show that the superhelical geometry can be altered by carefully placed amino acid substitutions, and we examine how these sequence changes affect intrinsic repeat stability and inter-repeat coupling. Our findings provide the means to dissect and modulate repeat-protein stability and dynamics, which will be essential for researchers to understand the function of natural repeat proteins and to exploit artificial repeats proteins in nanotechnology and biomedical applications.
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Affiliation(s)
- Marie Synakewicz
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom†
| | - Rohan S Eapen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom†
| | - Albert Perez-Riba
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom†
| | - Pamela J E Rowling
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom†
| | - Daniela Bauer
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Andreas Weißl
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Gerhard Fischer
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Marko Hyvönen
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Matthias Rief
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Laura S Itzhaki
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom†
| | - Johannes Stigler
- Gene Center Munich, Ludwig-Maximilians-Universität München, Feodor-Lynen-Straße 25, 81377 München, Germany
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2
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Synakewicz M, Eapen RS, Perez-Riba A, Rowling PJE, Bauer D, Weißl A, Fischer G, Hyvönen M, Rief M, Itzhaki LS, Stigler J. Unraveling the Mechanics of a Repeat-Protein Nanospring: From Folding of Individual Repeats to Fluctuations of the Superhelix. ACS NANO 2022; 16:3895-3905. [PMID: 35258937 PMCID: PMC8944806 DOI: 10.1021/acsnano.1c09162] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Tandem-repeat proteins comprise small secondary structure motifs that stack to form one-dimensional arrays with distinctive mechanical properties that are proposed to direct their cellular functions. Here, we use single-molecule optical tweezers to study the folding of consensus-designed tetratricopeptide repeats (CTPRs), superhelical arrays of short helix-turn-helix motifs. We find that CTPRs display a spring-like mechanical response in which individual repeats undergo rapid equilibrium fluctuations between partially folded and unfolded conformations. We rationalize the force response using Ising models and dissect the folding pathway of CTPRs under mechanical load, revealing how the repeat arrays form from the center toward both termini simultaneously. Most strikingly, we also directly observe the protein's superhelical tertiary structure in the force signal. Using protein engineering, crystallography, and single-molecule experiments, we show that the superhelical geometry can be altered by carefully placed amino acid substitutions, and we examine how these sequence changes affect intrinsic repeat stability and inter-repeat coupling. Our findings provide the means to dissect and modulate repeat-protein stability and dynamics, which will be essential for researchers to understand the function of natural repeat proteins and to exploit artificial repeats proteins in nanotechnology and biomedical applications.
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Affiliation(s)
- Marie Synakewicz
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Rohan S. Eapen
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Albert Perez-Riba
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Pamela J. E. Rowling
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Daniela Bauer
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Andreas Weißl
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Gerhard Fischer
- Department
of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Marko Hyvönen
- Department
of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Matthias Rief
- Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Laura S. Itzhaki
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Johannes Stigler
- Gene
Center Munich, Ludwig-Maximilians-Universität
München, Feodor-Lynen-Straße 25, 81377 München, Germany
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Freitag M, Kamp D, Synakewicz M, Stigler J. Identification and correction of miscalibration artifacts based on force noise for optical tweezers experiments. J Chem Phys 2021; 155:175101. [PMID: 34742205 DOI: 10.1063/5.0063690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Single-molecule force spectroscopy using optical tweezers continues to provide detailed insights into the behavior of nanoscale systems. Obtaining precise measurements of their mechanical properties is highly dependent on accurate instrument calibration. Therefore, instrumental drift or inaccurate calibration may prevent reaching an accuracy at the theoretical limit and may lead to incorrect conclusions. Commonly encountered sources of error include inaccuracies in the detector sensitivity and trap stiffness and neglecting the non-harmonicity of an optical trap at higher forces. Here, we first quantify the impact of these artifacts on force-extension data and find that a small deviation of the calibration parameters can already have a significant downstream effect. We then develop a method to identify and remove said artifacts based on differences in the theoretical and measured noise of bead fluctuations. By applying our procedure to both simulated and experimental data, we can show how effects due to miscalibration and trap non-linearities can be successfully removed. Most importantly, this correction can be performed post-measurement and could be adapted for data acquired using any force spectroscopy technique.
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Affiliation(s)
- Marvin Freitag
- Gene Center, Ludwig-Maximilians-University, Munich 81377, Germany
| | - Dieter Kamp
- Gene Center, Ludwig-Maximilians-University, Munich 81377, Germany
| | - Marie Synakewicz
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Johannes Stigler
- Gene Center, Ludwig-Maximilians-University, Munich 81377, Germany
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