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Stenzoski NE, Zou J, Piserchio A, Ghose R, Holehouse AS, Raleigh DP. The Cold-Unfolded State Is Expanded but Contains Long- and Medium-Range Contacts and Is Poorly Described by Homopolymer Models. Biochemistry 2020; 59:3290-3299. [PMID: 32786415 DOI: 10.1021/acs.biochem.0c00469] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cold unfolding of proteins is predicted by the Gibbs-Helmholtz equation and is thought to be driven by a strongly temperature-dependent interaction of protein nonpolar groups with water. Studies of the cold-unfolded state provide insight into protein energetics, partially structured states, and folding cooperativity and are of practical interest in biotechnology. However, structural characterization of the cold-unfolded state is much less extensive than studies of thermally or chemically denatured unfolded states, in large part because the midpoint of the cold unfolding transition is usually below freezing. We exploit a rationally designed point mutation (I98A) in the hydrophobic core of the C-terminal domain of the ribosomal protein L9 that allows the cold denatured state ensemble to be observed above 0 °C at near neutral pH and ambient pressure in the absence of added denaturants. A combined approach consisting of paramagnetic relaxation enhancement measurements, analysis of small-angle X-ray scattering data, all-atom simulations, and polymer theory provides a detailed description of the cold-unfolded state. Despite a globally expanded ensemble, as determined by small-angle X-ray scattering, sequence-specific medium- and long-range interactions in the cold-unfolded state give rise to deviations from homopolymer-like behavior. Our results reveal that the cold-denatured state is heterogeneous with local and long-range intramolecular interactions that may prime the folded state and also demonstrate that significant long-range interactions are compatible with expanded unfolded ensembles. The work also highlights the limitations of homopolymer-based descriptions of unfolded states of proteins.
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Affiliation(s)
- Natalie E Stenzoski
- Graduate Program in Biochemistry & Structural Biology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Junjie Zou
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Andrea Piserchio
- Department of Chemistry and Biochemistry, The City College of New York, New York, New York 10031, United States
| | - Ranajeet Ghose
- Department of Chemistry and Biochemistry, The City College of New York, New York, New York 10031, United States.,Graduate Programs in Biochemistry, Chemistry and Physics, The Graduate Center of CUNY, New York, New York 10016, United States
| | - Alex S Holehouse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, United States.,Center for Science and Engineering of Living Systems, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Daniel P Raleigh
- Graduate Program in Biochemistry & Structural Biology, Stony Brook University, Stony Brook, New York 11794-3400, United States.,Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States.,Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Zhang S, Zhang Y, Stenzoski NE, Zou J, Peran I, McCallum SA, Raleigh DP, Royer CA. Pressure-Temperature Analysis of the Stability of the CTL9 Domain Reveals Hidden Intermediates. Biophys J 2019; 116:445-453. [PMID: 30685054 DOI: 10.1016/j.bpj.2019.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 12/13/2018] [Accepted: 01/02/2019] [Indexed: 11/30/2022] Open
Abstract
The observation of two-state unfolding for many small single-domain proteins by denaturants has led to speculation that protein sequences may have evolved to limit the population of partially folded states that could be detrimental to fitness. How such strong cooperativity arises from a multitude of individual interactions is not well understood. Here, we investigate the stability and folding cooperativity of the C-terminal domain of the ribosomal protein L9 in the pressure-temperature plane using site-specific NMR. In contrast to apparent cooperative unfolding detected with denaturant-induced and thermal-induced unfolding experiments and stopped-flow refolding studies at ambient pressure, NMR-detected pressure unfolding revealed significant deviation from two-state behavior, with a core region that was selectively destabilized by increasing temperature. Comparison of pressure-dependent NMR signals from both the folded and unfolded states revealed the population of at least one invisible excited state at atmospheric pressure. The core destabilizing cavity-creating I98A mutation apparently increased the cooperativity of the loss of folded-state peak intensity while also increasing the population of this invisible excited state present at atmospheric pressure. These observations highlight how local stability is subtly modulated by sequence to tune protein conformational landscapes and illustrate the ability of pressure- and temperature-dependent studies to reveal otherwise hidden states.
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Affiliation(s)
- Siwen Zhang
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York
| | - Yi Zhang
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York
| | - Natalie E Stenzoski
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York
| | - Junjie Zou
- Department of Chemistry, Stony Brook University, Stony Brook, New York; Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York
| | - Ivan Peran
- Department of Chemistry, Stony Brook University, Stony Brook, New York
| | | | - Daniel P Raleigh
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York; Department of Chemistry, Stony Brook University, Stony Brook, New York; Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York; Institue of Structural and Molecular Biology, University College London, London, United Kingdom.
| | - Catherine A Royer
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York; Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York.
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Stenzoski NE, Luan B, Holehouse AS, Raleigh DP. The Unfolded State of the C-Terminal Domain of L9 Expands at Low but Not at Elevated Temperatures. Biophys J 2018; 115:655-663. [PMID: 30098729 DOI: 10.1016/j.bpj.2018.07.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/13/2018] [Accepted: 07/17/2018] [Indexed: 11/26/2022] Open
Abstract
The temperature dependence of the overall dimensions of the denatured state ensemble (DSE) of proteins remains unclear. Some studies indicate compaction of the DSE at high temperatures, whereas others argue that dimensions do not decrease. The degree of compaction or expansion in the cold-denatured state has been less studied. To investigate the temperature dependence of unfolded state dimensions, small angle x-ray scattering measurements were performed in native buffer in the absence of denaturant for a designed point mutant of the C-terminal domain of L9, a small cooperatively folded α-β protein, at 14 different temperatures over the range of 5-60°C. The I98A mutation destabilizes the domain such that both the DSE and the folded state are populated at 25°C in the absence of denaturant or extreme pH. Thermal unfolding as well as cold unfolding can thus be observed in the absence of denaturant, allowing a direct comparison of these regimes for the same protein using the same technique. The temperature of maximal stability, Ts, is 30°C. There is no detectable change in Rg of the unfolded state as the temperature is increased above Ts, but a clear expansion is detected as the temperature is decreased below Ts. The Rg of the DSE populated in buffer was found to be 27.8 ± 1.7 Å at 5°C, 21.8 ± 1.9 Å at 30°C, and 21.7 ± 2.0 Å at 60°C. In contrast, no significant temperature dependence was observed for the value of Rg measured in 6 M guanidine hydrochloride. The small angle x-ray scattering data reported here indicate clear differences between the cold- and thermal-unfolded states and show that there is no significant compaction at elevated temperatures.
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Affiliation(s)
- Natalie E Stenzoski
- Graduate Program in Biochemistry & Structural Biology, Stony Brook, New York
| | - Bowu Luan
- Department of Chemistry, Stony Brook University, Stony Brook, New York
| | - Alex S Holehouse
- Center for Biological Systems Engineering, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Daniel P Raleigh
- Graduate Program in Biochemistry & Structural Biology, Stony Brook, New York; Department of Chemistry, Stony Brook University, Stony Brook, New York; Institute of Structural and Molecular Biology, University of College London, London, United Kingdom.
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Stenzoski NE, Rogozea AL, Koerner MM, Ray BD, Petrache HI. Membrane Interactions in Ionic Solutions. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.4266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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