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Sun H, Yao C, You K, Chen C, Liu S, Xu Z. Nanopore single-molecule biosensor in protein denaturation analysis. Anal Chim Acta 2023; 1243:340830. [PMID: 36697181 DOI: 10.1016/j.aca.2023.340830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/02/2023] [Accepted: 01/11/2023] [Indexed: 01/13/2023]
Abstract
Unclear issues in protein studies include but not limited to the stability and denaturation mechanism in the presence of denaturants. Herein, we report a dynamic monitoring approach based on nanopore single-molecule biosensor, which can detect the protein's folding and unfolding transitions by recording a nanopore ionic current. When gradually increasing the concentration of denaturant guanidine hydrochloride (GdmCl), sensitive responses were observed with lysozyme unfolding. The emergence of the featured biphasic-pulse demonstrated the existence of a stable intermediate. It was the first time to experimentally confirm the dynamic equilibrium between the intermediate and the native states at single molecule level, therefore consolidating the standpoint of lysozyme denaturation process following the three-state model. Additionally, we got more insights into the conformation about the intermediate as globular-like structure, larger gyration radius, and enhanced positive charge density. We considered that the manner of denaturant toward lysozyme adopts the "direct" model based on stronger electrostatic and van der Waals forces. Nanopore biosensor exhibited excellent sensitivity with a low detection concentration of 280 pM and reproducibility in analysing the folding intermediate of lysozyme.
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Affiliation(s)
- Hong Sun
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China.
| | - Chuan Yao
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China
| | - Kaibo You
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China
| | - Can Chen
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China
| | - Shuoshuo Liu
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China
| | - Zhihong Xu
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Henan, 461000, PR China
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Miyazaki Y, Kikuchi M, Umezawa K, Descamps A, Nakamura D, Furuie G, Sumida T, Saito K, Kimura N, Niwa T, Sumida Y, Umehara T, Hosoya T, Kii I. Structure-activity relationship for the folding intermediate-selective inhibition of DYRK1A. Eur J Med Chem 2022; 227:113948. [PMID: 34742017 DOI: 10.1016/j.ejmech.2021.113948] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/21/2021] [Accepted: 10/21/2021] [Indexed: 01/06/2023]
Abstract
DYRK1A phosphorylates proteins involved in neurological disorders in an intermolecular manner. Meanwhile, during the protein folding process of DYRK1A, a transitional folding intermediate catalyzes the intramolecular autophosphorylation required for the "one-off" inceptive activation and stabilization. In our previous study, a small molecule termed FINDY (1) was identified, which inhibits the folding intermediate-catalyzed intramolecular autophosphorylation of DYRK1A but not the folded state-catalyzed intermolecular phosphorylation. However, the structural features of FINDY (1) responsible for this intermediate-selective inhibition remain elusive. In this study, structural derivatives of FINDY (1) were designed and synthesized according to its predicted binding mode in the ATP pocket of DYRK1A. Quantitative structure-activity relationship (QSAR) of the derivatives revealed that the selectivity against the folding intermediate is determined by steric hindrance between the bulky hydrophobic moiety of the derivatives and the entrance to the pocket. In addition, a potent derivative 3 was identified, which inhibited the folding intermediate more strongly than FINDY (1); it was designated as dp-FINDY. Although dp-FINDY (3) did not inhibit the folded state, as well as FINDY (1), it inhibited the intramolecular autophosphorylation of DYRK1A in an in vitro cell-free protein synthesis assay. Furthermore, dp-FINDY (3) destabilized endogenous DYRK1A in HEK293 cells. This study provides structural insights into the folding intermediate-selective inhibition of DYRK1A and expands the chemical options for the design of a kinase inhibitor.
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Affiliation(s)
- Yuka Miyazaki
- Laboratory for Drug Target Research, Department of Agriculture, Graduate School of Science and Technology, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan
| | - Masaki Kikuchi
- Laboratory for Epigenetics Drug Discovery, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Koji Umezawa
- Department of Biomolecular Innovation, Institute for Biomedical Sciences, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan
| | - Aurelie Descamps
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Daichi Nakamura
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Gaku Furuie
- Laboratory for Drug Target Research, Department of Agriculture, Graduate School of Science and Technology, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan
| | - Tomoe Sumida
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Kanako Saito
- Laboratory for Drug Target Research, Department of Agriculture, Graduate School of Science and Technology, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan
| | - Ninako Kimura
- Laboratory for Drug Target Research, Department of Agriculture, Graduate School of Science and Technology, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan
| | - Takashi Niwa
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Yuto Sumida
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Takashi Umehara
- Laboratory for Epigenetics Drug Discovery, RIKEN Center for Biosystems Dynamics Research, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Takamitsu Hosoya
- Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan; Laboratory of Chemical Bioscience, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (TMDU), 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan
| | - Isao Kii
- Laboratory for Drug Target Research, Department of Agriculture, Graduate School of Science and Technology, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan; Department of Biomolecular Innovation, Institute for Biomedical Sciences, Shinshu University, 8304 Minami-Minowa, Kami-Ina, Nagano, 399-4598, Japan; Laboratory for Chemical Biology, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
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Tompa DR, Muthusamy S, Srikanth S, Kadhirvel S. Molecular dynamics of far positioned surface mutations of Cu/Zn SOD1 promotes altered structural stability and metal-binding site: Structural clues to the pathogenesis of amyotrophic lateral sclerosis. J Mol Graph Model 2020; 100:107678. [PMID: 32768728 DOI: 10.1016/j.jmgm.2020.107678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 06/18/2020] [Accepted: 06/26/2020] [Indexed: 10/23/2022]
Abstract
Cu/Zn superoxide dismutase (SOD1) mutations are associated to the motor neuron disorder, amyotrophic lateral sclerosis (ALS), which is characterized by aggregates of the misfolded proteins. The distribution of mutations all over the three-dimensional structure of SOD1 makes it complex to determine the exact molecular mechanism underlying SOD1 destabilization and the associated ALS pathology. In this study, we have examined structure and dynamics of SOD1 protein upon two ALS associated point mutations at the surface residue Glu100 (E100G and E100K), which is located far from the Cu and Zn sites and dimer interface. The molecular dynamics simulations were performed for these mutants for 50ns using GROMACS package. Our results indicate that the mutations result in structural destabilization by affecting the gate keeping role of Glu100 and loss of electrostatic interactions on the protein surface which stabilizes the β-barrel structure of the native form. Further, these mutations could increase the fluctuations in the zinc-binding loop (loop IV), primarily due to loss of hydrogen bond between Asp101 and Arg79. The relaxed conformation of Arg79 further affects the native conformation of His80 and Asp83, that results in altered zinc site geometry and the structure of the substrate channel. Our results clearly suggest that, similar to the mutations located at metal sites/dimer interface/disulfide regions, the mutations at the far positioned site (Glu100) also induce significant conformational changes that could affect the metallation and structure of SOD1 molecule, resulting in formation of toxic intermediate species that cause ALS.
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Affiliation(s)
- Dharma Rao Tompa
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613401, Tamil Nadu, India
| | - Sureshan Muthusamy
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613401, Tamil Nadu, India
| | - Srimari Srikanth
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613401, Tamil Nadu, India
| | - Saraboji Kadhirvel
- Biomolecular Crystallography Laboratory, Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613401, Tamil Nadu, India.
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Sekhon G, Singh R. Human aldose reductase unfolds through an intermediate. F1000Res 2019; 8:564. [PMID: 31723418 PMCID: PMC6844136 DOI: 10.12688/f1000research.18963.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/22/2019] [Indexed: 11/26/2022] Open
Abstract
Background: Human aldose reductase (hAR) is the first and rate-limiting enzyme of the polyol pathway. For the development of secondary complications of diabetes in chronic hyperglycemic conditions, one of the critical factors is the increased flux of glucose through the polyol pathway. Due to this clinical implication, hAR attracted considerable attention from the drug discovery perspective. In spite of extensive characterization in the context of biochemical and structural aspects, we know very little about the unfolding behavior of hAR. This study reports equilibrium unfolding studies of hAR. Methods: We carried out thermal denaturation and chemical-induced equilibrium unfolding studies of hAR monitored by circular dichroism and fluorescence spectroscopy. Results: Thermal denaturation studies presented a classical picture of two-state unfolding from native to the denatured state. The data was used to derive thermodynamic parameters and study the thermostability of hAR. Chemical induced equilibrium unfolding studies led us to discover an intermediate state, which gets populated at 3.5-4.0 M and 0.7-2.0 M of urea and GuHCl, respectively. Thermodynamic parameters derived from chemical-induced unfolding are in agreement with those obtained from thermal denaturation of hAR. Conclusion: This study revealed that aldose reductase unfolds from native to the unfolded state via an intermediate. Assessment of the thermodynamic stability of native, intermediate, and unfolded states shows that significant energy barriers separate these states, which ensures the cooperativity of unfolding. As hAR functions in cells that are under osmotic and oxidative stress, these
in vitro findings may have implications for its native conformation under the physiological state.
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Affiliation(s)
- Gurprit Sekhon
- Department cum National Center for Human Genome Studies and Research, Panjab University, Chandigarh, 160014, India
| | - Ranvir Singh
- Department cum National Center for Human Genome Studies and Research, Panjab University, Chandigarh, 160014, India
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Ge B, Jiang X, Chen Y, Sun T, Yang Q, Huang F. Kinetic and thermodynamic studies reveal chemokine homologues CC11 and CC24 with an almost identical tertiary structure have different folding pathways. BMC Biophys 2017; 10:7. [PMID: 28919974 PMCID: PMC5596964 DOI: 10.1186/s13628-017-0039-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 09/06/2017] [Indexed: 11/10/2022]
Abstract
BACKGROUND Proteins with low sequence identity but almost identical tertiary structure and function have been valuable to uncover the relationship between sequence, tertiary structure, folding mechanism and functions. Two homologous chemokines, CCL11 and CCL24, with low sequence identity but similar tertiary structure and function, provide an excellent model system for respective studies. RESULTS The kinetics and thermodynamics of the two homologous chemokines were systematically characterized. Despite their similar tertiary structures, CCL11 and CCL24 show different thermodynamic stability in guanidine hydrochloride titration, with D50% = 2.20 M and 4.96 M, respectively. The kinetics curves clearly show two phases in the folding/unfolding processes of both CCL11 and CCL24, which suggests the existence of an intermediate state in their folding/unfolding processes. The folding pathway of both CCL11 and CCL24 could be well described using a folding model with an on-pathway folding intermediate. However, the folding kinetics and stability of the intermediate state of CCL11 and CCL24 are obviously different. CONCLUSION Our results suggest homologous proteins with low sequence identity can display almost identical tertiary structure, but very different folding mechanisms, which applies to homologues in the chemokine protein family, extending the general applicability of the above observation.
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Affiliation(s)
- Baosheng Ge
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
| | - Xiaoyong Jiang
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
| | - Yao Chen
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
| | - Tingting Sun
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
| | - Qiuxia Yang
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
| | - Fang Huang
- Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580 People's Republic of China
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Petrosino M, Bonetti D, Pasquo A, Lori L, Chiaraluce R, Consalvi V, Travaglini-Allocatelli C. Unveiling the folding mechanism of the Bromodomains. Biochem Biophys Rep 2017; 11:99-104. [PMID: 28955774 PMCID: PMC5614698 DOI: 10.1016/j.bbrep.2017.06.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 03/29/2017] [Revised: 06/23/2017] [Accepted: 06/28/2017] [Indexed: 12/19/2022] Open
Abstract
Bromodomains (BRDs) are small protein domains often present in large multidomain proteins involved in transcriptional regulation in eukaryotic cells. They currently represent valuable targets for the development of inhibitors of aberrant transcriptional processes in a variety of human diseases. Here we report urea-induced equilibrium unfolding experiments monitored by circular dichroism (CD) and fluorescence on two structurally similar BRDs: BRD2(2) and BRD4(1), showing that BRD4(1) is more stable than BRD2(2). Moreover, we report a description of their kinetic folding mechanism, as obtained by careful analysis of stopped-flow and temperature-jump data. The presence of a high energy intermediate for both proteins, suggested by the non-linear dependence of the folding rate on denaturant concentration in the millisec time regime, has been experimentally observed by temperature-jump experiments. Quantitative global analysis of all the rate constants obtained over a wide range of urea concentrations, allowed us to propose a common, three-state, folding mechanism for these two BRDs. Interestingly, the intermediate of BRD4(1) appears to be more stable and structurally native-like than that populated by BRD2(2). Our results underscore the role played by structural topology and sequence in determining and tuning the folding mechanism. A three-state mechanism for the folding of two representative Bromodomains is proposed. Global analyses of BRD2(2) and BRD4(1) folding kinetics highlights the presence of an on-pathway, folding intermediate. The folding intermediate of BRD4(1) is proposed to be more native-like than that of BRD2(2).
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Affiliation(s)
- Maria Petrosino
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
| | - Daniela Bonetti
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
| | | | - Laura Lori
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
| | - Roberta Chiaraluce
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
| | - Valerio Consalvi
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
| | - Carlo Travaglini-Allocatelli
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Università di Roma “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
- Corresponding author.
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7
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Ghadami SA, Bemporad F, Sala BM, Tiana G, Ricagno S, Chiti F. FRET studies of various conformational states adopted by transthyretin. Cell Mol Life Sci 2017; 74:3577-3598. [PMID: 28478513 DOI: 10.1007/s00018-017-2533-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 04/15/2017] [Accepted: 05/02/2017] [Indexed: 01/01/2023]
Abstract
Transthyretin (TTR) is an extracellular protein able to deposit into well-defined protein aggregates called amyloid, in pathological conditions known as senile systemic amyloidosis, familial amyloid polyneuropathy, familial amyloid cardiomyopathy and leptomeningeal amyloidosis. At least three distinct partially folded states have been described for TTR, including the widely studied amyloidogenic state at mildly acidic pH. Here, we have used fluorescence resonance energy transfer (FRET) experiments in a monomeric variant of TTR (M-TTR) and in its W41F and W79F mutants, taking advantage of the presence of a unique, solvent-exposed, cysteine residue at position 10, that we have labelled with a coumarin derivative (DACM, acceptor), and of the two natural tryptophan residues at positions 41 and 79 (donors). Trp41 is located in an ideal position as it is one of the residues of β-strand C, whose degree of unfolding is debated. We found that the amyloidogenic state at low pH has the same FRET efficiency as the folded state at neutral pH in both M-TTR and W79F-M-TTR, indicating an unmodified Cys10-Trp41 distance. The partially folded state populated at low denaturant concentrations also has a similar FRET efficiency, but other spectroscopic probes indicate that it is distinct from the amyloidogenic state at acidic pH. By contrast, the off-pathway state accumulating transiently during refolding has a higher FRET efficiency, indicating non-native interactions that reduce the Cys10-Trp41 spatial distance, revealing a third distinct conformational state. Overall, our results clarify a negligible degree of unfolding of β-strand C in the formation of the amyloidogenic state and establish the concept that TTR is a highly plastic protein able to populate at least three distinct conformational states.
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Affiliation(s)
- Seyyed Abolghasem Ghadami
- Dipartimento di Scienze Biomediche Sperimentali e Cliniche "Mario Serio", Sezione di Scienze Biochimiche, Università degli Studi di Firenze, Viale Morgagni 50, 50134, Florence, Italy
| | - Francesco Bemporad
- Dipartimento di Scienze Biomediche Sperimentali e Cliniche "Mario Serio", Sezione di Scienze Biochimiche, Università degli Studi di Firenze, Viale Morgagni 50, 50134, Florence, Italy
| | - Benedetta Maria Sala
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Guido Tiana
- Center for Complexity and Biosystems, Department of Physics, Università degli Studi di Milano and INFN, via Celoria 16, 20133, Milan, Italy
| | - Stefano Ricagno
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Fabrizio Chiti
- Dipartimento di Scienze Biomediche Sperimentali e Cliniche "Mario Serio", Sezione di Scienze Biochimiche, Università degli Studi di Firenze, Viale Morgagni 50, 50134, Florence, Italy.
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Kölbel K, Weininger U, Ihling C, Mrestani-Klaus C, Ulbrich-Hofmann R. Native state dynamics affects the folding transition of porcine pancreatic phospholipase A2. Biophys Chem 2015; 206:12-21. [PMID: 26117657 DOI: 10.1016/j.bpc.2015.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/11/2015] [Accepted: 06/14/2015] [Indexed: 11/23/2022]
Abstract
Porcine pancreatic phospholipase A2, a small and disulfide rich protein, is extremely resistant against chemically or thermally induced unfolding. Despite this marked resistance, the protein displays broad unfolding transitions resulting in comparatively low apparent thermodynamic stability. Broad unfolding transitions may result from undetected folding intermediates, residual structures in the unfolded state or an inhomogeneity of the native state. Using circular dichroism, fluorescence, and NMR spectroscopy, we ruled out the existence of stably populated folding intermediates, whereas UV absorbance measurements hinted at stable residual structures in the unfolded state. These residual structures proved, however, to have no impact on the folding parameters. Studies by limited proteolysis, CD, and NMR spectroscopy under non-denaturing conditions suggested pronounced dynamics of the protein in the native state, which as long as unrestrained by acidic pH or bound Ca(2+) ions exert considerable influence on the unfolding transition.
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9
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Fotouhi L, Yousefinejad S, Salehi N, Saboury AA, Sheibani N, Moosavi-Movahedi AA. Application of merged spectroscopic data combined with chemometric analysis for resolution of hemoglobin intermediates during chemical unfolding. Spectrochim Acta A Mol Biomol Spectrosc 2015; 136 Pt C:1974-1981. [PMID: 25468440 PMCID: PMC6690049 DOI: 10.1016/j.saa.2014.10.120] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 10/21/2014] [Accepted: 10/28/2014] [Indexed: 06/04/2023]
Abstract
Using tetradecyltrimethylammonium bromide (TTAB) as a surfactant denaturant, and augmentation of different spectroscopic data, helped to detect the intermediates of hemoglobin (Hb) during unfolding process. UV-vis, fluorescence, and circular dichroism spectroscopy were used simultaneously to monitor different aspects of hemoglobin species from the tertiary or secondary structure points of view. Application of the multivariate curve resolution-alternating least square (MCR-ALS), using the initial estimates of spectral profiles and appropriate constraints on different parts of augmented spectroscopic data, showed good efficiency for characterization of intermediates during Hb unfolding. These results indicated the existence of five protein species, including three intermediate-like compounds in this process. The unfolding pathway in the presence of TTAB included conversion of oxyhemoglobin into deoxyhemoglobin, and then ferrylhemoglobin, ferrihemoglobin or aquamethemoglobin, which finally transformed into hemichrome. This is the first application of chemometric analysis on the merged spectroscopic data related to chemical denaturation of a protein. These types of analysis in multisubunit proteins not only increase the domain of information, but also can reduce the ambiguities of the obtained results.
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Affiliation(s)
- L Fotouhi
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - S Yousefinejad
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - N Salehi
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - A A Saboury
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran; Center of Excellence in Biothermodynamics, University of Tehran, Tehran, Iran
| | - N Sheibani
- Department of Ophthalmology and Visual Sciences and McPherson Eye Research Institute, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
| | - A A Moosavi-Movahedi
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran; Center of Excellence in Biothermodynamics, University of Tehran, Tehran, Iran.
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Serebryany E, King JA. The βγ-crystallins: native state stability and pathways to aggregation. Prog Biophys Mol Biol 2014; 115:32-41. [PMID: 24835736 DOI: 10.1016/j.pbiomolbio.2014.05.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/30/2014] [Accepted: 05/02/2014] [Indexed: 01/26/2023]
Abstract
The βγ-crystallins are among the most stable and long-lived proteins in the human body. With increasing age, however, they transform to high molecular weight light-scattering aggregates, resulting in cataracts. This occurs despite the presence in the lens of high concentrations of the a-crystallin chaperones. Aggregation of crystallins can be induced in vitro by a variety of stresses, including acidic pH, ultraviolet light, oxidative damage, heating or freezing, and specific amino acid substitutions. Accumulating evidence points to the existence of specific biochemical pathways of protein: protein interaction and polymerization. We review the methods used for studying crystallin stability and aggregation and discuss the sometimes counterintuitive relationships between factors that favor native state stability and those that favor non-native aggregation. We discuss the behavior of βγ-crystallins in mixtures and their chaperone ability; the consequences of missense mutations and covalent damage to the side-chains; and the evolutionary strategies that have shaped these proteins. Efforts are ongoing to reveal the nature of cataractous crystallin aggregates and understand the mechanisms of aggregation in the context of key models of protein polymerization: amyloid, native-state, and domain-swapped. Such mechanistic understanding is likely to be of value for the development of therapeutic interventions and draw attention to unanswered questions about the relationship between a protein's native state stability and its transformation to an aggregated state.
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Affiliation(s)
- Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States.
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