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Zhuo Y, Li X, He Z, Lu M. Pathological mechanisms of neuroimmune response and multitarget disease-modifying therapies of mesenchymal stem cells in Parkinson's disease. Stem Cell Res Ther 2023; 14:80. [PMID: 37041580 PMCID: PMC10091615 DOI: 10.1186/s13287-023-03280-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 03/13/2023] [Indexed: 04/13/2023] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disease characterized by the degeneration of dopaminergic neurons in the substantia nigra (SN); the etiology and pathological mechanism of the disease are still unclear. Recent studies have shown that the activation of a neuroimmune response plays a key role in the development of PD. Alpha-synuclein (α-Syn), the primary pathological marker of PD, can gather in the SN and trigger a neuroinflammatory response by activating microglia which can further activate the dopaminergic neuron's neuroimmune response mediated by reactive T cells through antigen presentation. It has been shown that adaptive immunity and antigen presentation processes are involved in the process of PD and further research on the neuroimmune response mechanism may open new methods for its prevention and therapy. While current therapeutic regimens are still focused on controlling clinical symptoms, applications such as immunoregulatory strategies can delay the symptoms and the process of neurodegeneration. In this review, we summarized the progression of the neuroimmune response in PD based on recent studies and focused on the use of mesenchymal stem cell (MSC) therapy and challenges as a strategy of disease-modifying therapy with multiple targets.
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Affiliation(s)
- Yi Zhuo
- Department of Neurosurgery, The Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University/Hunan Cancer Hospital, Changsha, 410000, Hunan, China
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, 410006, Hunan, China
| | - Xuan Li
- Department of Neurosurgery, The Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University/Hunan Cancer Hospital, Changsha, 410000, Hunan, China
| | - Zhengwen He
- Department of Neurosurgery, The Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University/Hunan Cancer Hospital, Changsha, 410000, Hunan, China.
| | - Ming Lu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, 410006, Hunan, China.
- Hunan Provincial Key Laboratory of Neurorestoratology, The Second Affiliated Hospital (the 921st Hospital of PLA), Hunan Normal University, Changsha, 410003, Hunan, China.
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2
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N-alpha-acetylation of Huntingtin protein increases its propensity to aggregate. J Biol Chem 2021; 297:101363. [PMID: 34732320 PMCID: PMC8640455 DOI: 10.1016/j.jbc.2021.101363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/23/2021] [Accepted: 10/25/2021] [Indexed: 11/22/2022] Open
Abstract
Huntington’s disease (HD) is a neurodegenerative disorder caused by a poly-CAG expansion in the first exon of the HTT gene, resulting in an extended poly-glutamine tract in the N-terminal domain of the Huntingtin (Htt) protein product. Proteolytic fragments of the poly-glutamine–containing N-terminal domain form intranuclear aggregates that are correlated with HD. Post-translational modification of Htt has been shown to alter its function and aggregation properties. However, the effect of N-terminal Htt acetylation has not yet been considered. Here, we developed a bacterial system to produce unmodified or N-terminally acetylated and aggregation-inducible Htt protein. We used this system together with biochemical, biophysical, and imaging studies to confirm that the Htt N-terminus is an in vitro substrate for the NatA N-terminal acetyltransferase and show that N-terminal acetylation promotes aggregation. These studies represent the first link between N-terminal acetylation and the promotion of a neurodegenerative disease and implicates NatA-mediated Htt acetylation as a new potential therapeutic target in HD.
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3
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NMR unveils an N-terminal interaction interface on acetylated-α-synuclein monomers for recruitment to fibrils. Proc Natl Acad Sci U S A 2021; 118:2017452118. [PMID: 33903234 DOI: 10.1073/pnas.2017452118] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Amyloid fibril formation of α-synuclein (αS) is associated with multiple neurodegenerative diseases, including Parkinson's disease (PD). Growing evidence suggests that progression of PD is linked to cell-to-cell propagation of αS fibrils, which leads to seeding of endogenous intrinsically disordered monomer via templated elongation and secondary nucleation. A molecular understanding of the seeding mechanism and driving interactions is crucial to inhibit progression of amyloid formation. Here, using relaxation-based solution NMR experiments designed to probe large complexes, we probe weak interactions of intrinsically disordered acetylated-αS (Ac-αS) monomers with seeding-competent Ac-αS fibrils and seeding-incompetent off-pathway oligomers to identify Ac-αS monomer residues at the binding interface. Under conditions that favor fibril elongation, we determine that the first 11 N-terminal residues on the monomer form a common binding site for both fibrils and off-pathway oligomers. Additionally, the presence of off-pathway oligomers within a fibril seeding environment suppresses seeded amyloid formation, as observed through thioflavin-T fluorescence experiments. This highlights that off-pathway αS oligomers can act as an auto-inhibitor against αS fibril elongation. Based on these data taken together with previous results, we propose a model in which Ac-αS monomer recruitment to the fibril is driven by interactions between the intrinsically disordered monomer N terminus and the intrinsically disordered flanking regions (IDR) on the fibril surface. We suggest that this monomer recruitment may play a role in the elongation of amyloid fibrils and highlight the potential of the IDRs of the fibril as important therapeutic targets against seeded amyloid formation.
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Calvo JS, Mulpuri NV, Dao A, Qazi NK, Meloni G. Membrane insertion exacerbates the α-Synuclein-Cu(II) dopamine oxidase activity: Metallothionein-3 targets and silences all α-synuclein-Cu(II) complexes. Free Radic Biol Med 2020; 158:149-161. [PMID: 32712192 PMCID: PMC7484060 DOI: 10.1016/j.freeradbiomed.2020.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 07/03/2020] [Accepted: 07/05/2020] [Indexed: 10/23/2022]
Abstract
Copper binding to α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in substantia nigra dopaminergic neurons, potentiate its toxic redox-reactivity and plays a detrimental role in the etiology of Parkinson disease (PD). Soluble α-synuclein-Cu(II) complexes possess dopamine oxidase activity and catalyze ROS production in the presence of biological reducing agents via Cu(II)/Cu(I) redox cycling. These metal-centered redox reactivities harmfully promote the oxidation and oligomerization of α-Syn. While this chemistry has been investigated on recombinantly expressed soluble α-Syn, in vivo, α-Syn is acetylated at its N-terminus and is present in equilibrium between soluble and membrane-bound forms. This post-translational modification and membrane-binding alter the Cu(II) coordination environment and binding modes and are expected to affect the α-Syn-Cu(II) reactivity. In this work, we first investigated the reactivity of acetylated and membrane-bound complexes, and subsequently addressed whether the brain metalloprotein Zn7-metallothionein-3 (Zn7MT-3) possesses a multifaceted-role in targeting these aberrant copper interactions and consequent reactivity. Through biochemical characterization of the reactivity of the non-acetylated/N-terminally acetylated soluble or membrane-bound α-Syn-Cu(II) complexes towards dopamine, oxygen, and ascorbate, we reveal that membrane insertion dramatically exacerbates the catechol oxidase-like reactivity of α-Syn-Cu(II) as a result of a change in the Cu(II) coordination environment, thereby potentiating its toxicity. Moreover, we show that Zn7MT-3 can efficiently target all α-Syn-Cu(II) complexes through Cu(II) removal, preventing their deleterious redox activities. We demonstrate that the Cu(II) reduction by the thiolate ligands of Zn7MT-3 and the formation of Cu(I)4Zn4MT-3 featuring an unusual redox-inert Cu(I)4-thiolate cluster is the molecular mechanism responsible for the protective effect exerted by MT-3 towards α-Syn-Cu(II). This work provides the molecular basis for new therapeutic interventions to control the deleterious bioinorganic chemistry of α-Syn-Cu(II).
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Affiliation(s)
- Jenifer S Calvo
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Neha V Mulpuri
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Alex Dao
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Nabeeha K Qazi
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Gabriele Meloni
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA.
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5
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Abeyawardhane DL, Curry AM, Forney AK, Roberts JW, Lucas HR. Biometals as conformational modulators of α-synuclein photochemical crosslinking. J Biol Inorg Chem 2019; 24:1261-1268. [PMID: 31728738 PMCID: PMC7334974 DOI: 10.1007/s00775-019-01738-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 10/26/2019] [Indexed: 11/28/2022]
Abstract
Metal dyshomeostasis has long been linked to Parkinson's disease (PD), and the amyloidogenic protein α-synuclein (αS) is universally recognized as a key player in PD pathology. Structural consequences upon coordination of copper and iron to αS have gained attention due to significant dyshomeostasis of both metals in the PD brain. Protein-metal association can navigate protein folding in distinctive pathways based on the identity of the bio-metal in question. In this work, we employed photo-chemical crosslinking of unmodified proteins (PICUP) to evaluate these potential metal ion-induced structural alterations in the folding dynamics of N-terminally acetylated αS (NAcαS) following metal coordination. Through fluorescence analysis and immunoblotting analyses following photoirradiation, we discovered that coordination of iron obstructs copper-promoted crosslinking. The absence of intra-molecular crosslinking upon iron association further supports its C-terminal coordination site and suggests a potential role for iron in mitigating nearby post-translational modification of tyrosine residues. Decreased fluorescence emission upon synergistic coordination of both copper and iron highlighted that although copper acts as a conformational promotor of NAcαS crosslinking, iron inhibits analogous conformational changes within the protein. The metal coordination preferences of NAcαS suggest that both competitive binding sites as well as dual metal coordination contribute to the changes in folding dynamics, unveiling unique structural orientations for NAcαS that have a direct and measureable influence on photoinitiated dityrosine crosslinks. Moreover, our findings have physiological implications in that iron overload, as is associated with PD-insulted brain tissue, may serve as a conformational block of copper-promoted protein oxidation.
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Affiliation(s)
| | - Alyson M Curry
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA, 23284, USA
| | - Ashley K Forney
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA, 23284, USA
| | - Joel W Roberts
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA, 23284, USA
| | - Heather R Lucas
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA, 23284, USA.
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6
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Eldeeb MA, Fahlman RP, Ragheb MA, Esmaili M. Does N‐Terminal Protein Acetylation Lead to Protein Degradation? Bioessays 2019; 41:e1800167. [DOI: 10.1002/bies.201800167] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 08/12/2019] [Indexed: 12/29/2022]
Affiliation(s)
- Mohamed A. Eldeeb
- Department of Chemistry (Biochemistry Division)Faculty of ScienceCairo University Giza 12613 Egypt
- Department of Neurology and NeurosurgeryMontreal Neurological InstituteMcGill University Montreal Quebec H3A 2B4 Canada
| | - Richard P. Fahlman
- Department of BiochemistryUniversity of Alberta Edmonton Alberta T6G 2R3 Canada
| | - Mohamed A. Ragheb
- Department of Chemistry (Biochemistry Division)Faculty of ScienceCairo University Giza 12613 Egypt
| | - Mansoore Esmaili
- Department of BiochemistryUniversity of Alberta Edmonton Alberta T6G 2R3 Canada
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7
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González N, Gentile I, Garro HA, Delgado-Ocaña S, Ramunno CF, Buratti FA, Griesinger C, Fernández CO. Metal coordination and peripheral substitution modulate the activity of cyclic tetrapyrroles on αS aggregation: a structural and cell-based study. J Biol Inorg Chem 2019; 24:1269-1278. [PMID: 31486955 DOI: 10.1007/s00775-019-01711-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 07/28/2019] [Indexed: 12/11/2022]
Abstract
The discovery of aggregation inhibitors and the elucidation of their mechanism of action are key in the quest to mitigate the toxic consequences of amyloid formation. We have previously characterized the antiamyloidogenic mechanism of action of sodium phtalocyanine tetrasulfonate ([Na4(H2PcTS)]) on α-Synuclein (αS), demonstrating that specific aromatic interactions are fundamental for the inhibition of amyloid assembly. Here we studied the influence that metal preferential affinity and peripheral substituents may have on the activity of tetrapyrrolic compounds on αS aggregation. For the first time, our laboratory has extended the studies in the field of the bioinorganic chemistry and biophysics to cellular biology, using a well-established cell-based model to study αS aggregation. The interaction scenario described in our work revealed that both N- and C-terminal regions of αS represent binding interfaces for the studied compounds, a behavior that is mainly driven by the presence of negatively or positively charged substituents located at the periphery of the macrocycle. Binding modes of the tetrapyrrole ligands to αS are determined by the planarity and hydrophobicity of the aromatic ring system in the tetrapyrrolic molecule and/or the preferential affinity of the metal ion conjugated at the center of the macrocyclic ring. The different capability of phthalocyanines and meso-tetra (N-methyl-4-pyridyl) porphine tetrachloride ([H2PrTPCl4]) to modulate αS aggregation in vitro was reproduced in cell-based models of αS aggregation, demonstrating unequivocally that the modulation exerted by these compounds on amyloid assembly is a direct consequence of their interaction with the target protein.
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Affiliation(s)
- Nazareno González
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina
| | - Iñaki Gentile
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina
| | - Hugo A Garro
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina.,Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, CP 5700, San Luis, Argentina
| | - Susana Delgado-Ocaña
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina
| | - Carla F Ramunno
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina
| | - Fiamma A Buratti
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina
| | - Christian Griesinger
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Claudio O Fernández
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda, S2002LRK, Rosario, Argentina. .,Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.
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8
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Abeyawardhane DL, Heitger DR, Fernández RD, Forney AK, Lucas HR. C-Terminal Cu II Coordination to α-Synuclein Enhances Aggregation. ACS Chem Neurosci 2019; 10:1402-1410. [PMID: 30384594 DOI: 10.1021/acschemneuro.8b00448] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The structurally dynamic amyloidogenic protein α-synuclein (αS) is universally recognized as a key player in Parkinson's disease (PD). Copper, which acts as a neuronal signaling agent, is also an effector of αS structure, aggregation, and localization in vivo. In humans, αS is known to carry an acetyl group on the starting methionine residue, capping the N-terminal free amine which was a known high-affinity CuII binding site. We now report the first detailed characterization data using electron paramagnetic resonance (EPR) spectroscopy to describe the CuII coordination modes of N-terminally acetylated αS (NAcαS). Through use of EPR hyperfine structure analyses and the Peisach-Blumberg correlation, an N3O1 binding mode was established that involves the single histidine residue at position 50 and a lower population of a second CuII-binding mode that may involve a C-terminal contribution. We additionally generated an N-terminally acetylated disease-relevant variant, NAcH50Q, that promotes a shift in the CuII binding site to the C-terminus of the protein. Moreover, fibrillar NAcH50Q-CuII exhibits enhanced parallel β-sheet character and increased hydrophobic surface area compared to NAcαS-CuII and to both protein variants that lack a coordinated cupric ion. The results presented herein demonstrate the differential impact of distinct CuII binding sites within NAcαS, revealing that C-terminal CuII binding exacerbates the structural consequences of the H50Q missense mutation. Likewise, the global structural modifications that result from N-terminal capping augment the properties of CuII coordination. Hence, consideration of the effect of CuII on NAcαS and NAcH50Q misfolding may shed light on the extrinsic or environmental factors that influence PD pathology.
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Affiliation(s)
| | - Denver R. Heitger
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Ricardo D. Fernández
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Ashley K. Forney
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Heather R. Lucas
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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9
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Fernández RD, Lucas HR. Isolation of recombinant tetrameric N-acetylated α-synuclein. Protein Expr Purif 2018; 152:146-154. [DOI: 10.1016/j.pep.2018.07.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 07/10/2018] [Accepted: 07/19/2018] [Indexed: 12/25/2022]
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10
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Abeyawardhane DL, Fernández RD, Heitger DR, Crozier MK, Wolver JC, Lucas HR. Copper Induced Radical Dimerization of α-Synuclein Requires Histidine. J Am Chem Soc 2018; 140:17086-17094. [DOI: 10.1021/jacs.8b08947] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
| | - Ricardo D. Fernández
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Denver R. Heitger
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Madeleine K. Crozier
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Julia C. Wolver
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Heather R. Lucas
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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11
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Nguyen KT, Mun SH, Lee CS, Hwang CS. Control of protein degradation by N-terminal acetylation and the N-end rule pathway. Exp Mol Med 2018; 50:1-8. [PMID: 30054456 PMCID: PMC6063864 DOI: 10.1038/s12276-018-0097-y] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 04/11/2018] [Indexed: 11/10/2022] Open
Abstract
Nα-terminal acetylation (Nt-acetylation) occurs very frequently and is found in most proteins in eukaryotes. Despite the pervasiveness and universality of Nt-acetylation, its general functions in terms of physiological outcomes remain largely elusive. However, several recent studies have revealed that Nt-acetylation has a significant impact on protein stability, activity, folding patterns, cellular localization, etc. In addition, Nt-acetylation marks specific proteins for degradation by a branch of the N-end rule pathway, a subset of the ubiquitin-mediated proteolytic system. The N-end rule associates a protein's in vivo half-life with its N-terminal residue or modifications on its N-terminus. This review provides a current understanding of intracellular proteolysis control by Nt-acetylation and the N-end rule pathway.
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Affiliation(s)
- Kha The Nguyen
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Sang-Hyeon Mun
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Chang-Seok Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | - Cheol-Sang Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea.
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12
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Cieplak AS. Protein folding, misfolding and aggregation: The importance of two-electron stabilizing interactions. PLoS One 2017; 12:e0180905. [PMID: 28922400 PMCID: PMC5603215 DOI: 10.1371/journal.pone.0180905] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 06/22/2017] [Indexed: 12/17/2022] Open
Abstract
Proteins associated with neurodegenerative diseases are highly pleiomorphic and may adopt an all-α-helical fold in one environment, assemble into all-β-sheet or collapse into a coil in another, and rapidly polymerize in yet another one via divergent aggregation pathways that yield broad diversity of aggregates’ morphology. A thorough understanding of this behaviour may be necessary to develop a treatment for Alzheimer’s and related disorders. Unfortunately, our present comprehension of folding and misfolding is limited for want of a physicochemical theory of protein secondary and tertiary structure. Here we demonstrate that electronic configuration and hyperconjugation of the peptide amide bonds ought to be taken into account to advance such a theory. To capture the effect of polarization of peptide linkages on conformational and H-bonding propensity of the polypeptide backbone, we introduce a function of shielding tensors of the Cα atoms. Carrying no information about side chain-side chain interactions, this function nonetheless identifies basic features of the secondary and tertiary structure, establishes sequence correlates of the metamorphic and pH-driven equilibria, relates binding affinities and folding rate constants to secondary structure preferences, and manifests common patterns of backbone density distribution in amyloidogenic regions of Alzheimer’s amyloid β and tau, Parkinson’s α-synuclein and prions. Based on those findings, a split-intein like mechanism of molecular recognition is proposed to underlie dimerization of Aβ, tau, αS and PrPC, and divergent pathways for subsequent association of dimers are outlined; a related mechanism is proposed to underlie formation of PrPSc fibrils. The model does account for: (i) structural features of paranuclei, off-pathway oligomers, non-fibrillar aggregates and fibrils; (ii) effects of incubation conditions, point mutations, isoform lengths, small-molecule assembly modulators and chirality of solid-liquid interface on the rate and morphology of aggregation; (iii) fibril-surface catalysis of secondary nucleation; and (iv) self-propagation of infectious strains of mammalian prions.
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Affiliation(s)
- Andrzej Stanisław Cieplak
- Department of Chemistry, Bilkent University, Ankara, Turkey
- Department of Chemistry, Yale University, New Haven, Connecticut, United States of America
- Department of Chemistry, Brandeis University, Waltham, Massachusetts, United States of America
- * E-mail:
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13
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Pressure effects on α-synuclein amyloid fibrils: An experimental investigation on their dissociation and reversible nature. Arch Biochem Biophys 2017. [DOI: 10.1016/j.abb.2017.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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14
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Moriarty GM, Olson MP, Atieh TB, Janowska MK, Khare SD, Baum J. A pH-dependent switch promotes β-synuclein fibril formation via glutamate residues. J Biol Chem 2017; 292:16368-16379. [PMID: 28710275 DOI: 10.1074/jbc.m117.780528] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 07/11/2017] [Indexed: 01/10/2023] Open
Abstract
α-Synuclein (αS) is the primary protein associated with Parkinson's disease, and it undergoes aggregation from its intrinsically disordered monomeric form to a cross-β fibrillar form. The closely related homolog β-synuclein (βS) is essentially fibril-resistant under cytoplasmic physiological conditions. Toxic gain-of-function by βS has been linked to dysfunction, but the aggregation behavior of βS under altered pH is not well-understood. In this work, we compare fibril formation of αS and βS at pH 7.3 and mildly acidic pH 5.8, and we demonstrate that pH serves as an on/off switch for βS fibrillation. Using αS/βS domain-swapped chimera constructs and single residue substitutions in βS, we localized the switch to acidic residues in the N-terminal and non-amyloid component domains of βS. Computational models of βS fibril structures indicate that key glutamate residues (Glu-31 and Glu-61) in these domains may be sites of pH-sensitive interactions, and variants E31A and E61A show dramatically altered pH sensitivity for fibril formation supporting the importance of these charged side chains in fibril formation of βS. Our results demonstrate that relatively small changes in pH, which occur frequently in the cytoplasm and in secretory pathways, may induce the formation of βS fibrils and suggest a complex role for βS in synuclein cellular homeostasis and Parkinson's disease.
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Affiliation(s)
- Gina M Moriarty
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
| | - Michael P Olson
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
| | - Tamr B Atieh
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
| | - Maria K Janowska
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
| | - Sagar D Khare
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
| | - Jean Baum
- From the Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854
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Rossetti G, Musiani F, Abad E, Dibenedetto D, Mouhib H, Fernandez CO, Carloni P. Conformational ensemble of human α-synuclein physiological form predicted by molecular simulations. Phys Chem Chem Phys 2017; 18:5702-6. [PMID: 26553504 DOI: 10.1039/c5cp04549e] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We perform here enhanced sampling simulations of N-terminally acetylated human α-synuclein, an intrinsically disordered protein involved in Parkinson's disease. The calculations, consistent with experiments, suggest that the post-translational modification leads to the formation of a transient amphipathic α-helix. The latter, absent in the non-physiological form, alters protein dynamics at the N-terminal and intramolecular interactions.
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Affiliation(s)
- G Rossetti
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany. and Jülich Supercomputing Centre, Forschungszentrum Jülich, 52425 Jülich, Germany and Department of Oncology, Hematology and Stem Cell Transplantation, RWTH Aachen University, Aachen, Germany
| | - F Musiani
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany. and Scuola Internazionale Superiore di Studi Avanzati (SISSA/ISAS), via Bonomea 265, 34136 Trieste, Italy and Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, 40127 Bologna, Italy
| | - E Abad
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany. and German Research School for Simulation Sciences, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - D Dibenedetto
- German Research School for Simulation Sciences, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - H Mouhib
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | - C O Fernandez
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR), Universidad Nacional de Rosario, 27 de Febrero 210 bis, S2002LRK-Rosario, Argentina and Institute for Drug Discovery of Rosario (IIDEFAR), Universidad Nacional de Rosario, Rosario, 27 de Febrero 210 bis, S2002LRK-Rosario, Argentina
| | - P Carloni
- Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany. and German Research School for Simulation Sciences, Forschungszentrum Jülich, 52425 Jülich, Germany
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16
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Coordination and redox properties of copper interaction with α-synuclein. J Inorg Biochem 2016; 163:292-300. [DOI: 10.1016/j.jinorgbio.2016.04.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 03/11/2016] [Accepted: 04/04/2016] [Indexed: 11/23/2022]
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17
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Aksnes H, Drazic A, Marie M, Arnesen T. First Things First: Vital Protein Marks by N-Terminal Acetyltransferases. Trends Biochem Sci 2016; 41:746-760. [PMID: 27498224 DOI: 10.1016/j.tibs.2016.07.005] [Citation(s) in RCA: 172] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 07/01/2016] [Accepted: 07/08/2016] [Indexed: 11/28/2022]
Abstract
N-terminal (Nt) acetylation is known to be a highly abundant co-translational protein modification, but the recent discovery of Golgi- and chloroplast-resident N-terminal acetyltransferases (NATs) revealed that it can also be added post-translationally. Nt-acetylation may act as a degradation signal in a novel branch of the N-end rule pathway, whose functions include the regulation of human blood pressure. Nt-acetylation also modulates protein interactions, targeting, and folding. In plants, Nt-acetylation plays a role in the control of resistance to drought and in regulation of immune responses. Mutations of specific human NATs that decrease their activity can cause either the lethal Ogden syndrome or severe intellectual disability and cardiovascular defects. In sum, recent advances highlight Nt-acetylation as a key factor in many biological pathways.
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Affiliation(s)
- Henriette Aksnes
- Department of Molecular Biology, University of Bergen, 5020 Bergen, Norway
| | - Adrian Drazic
- Department of Molecular Biology, University of Bergen, 5020 Bergen, Norway
| | - Michaël Marie
- Department of Molecular Biology, University of Bergen, 5020 Bergen, Norway
| | - Thomas Arnesen
- Department of Molecular Biology, University of Bergen, 5020 Bergen, Norway; Department of Surgery, Haukeland University Hospital, 5021 Bergen, Norway.
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18
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Drazic A, Myklebust LM, Ree R, Arnesen T. The world of protein acetylation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1372-401. [PMID: 27296530 DOI: 10.1016/j.bbapap.2016.06.007] [Citation(s) in RCA: 509] [Impact Index Per Article: 63.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/04/2016] [Accepted: 06/08/2016] [Indexed: 12/30/2022]
Abstract
Acetylation is one of the major post-translational protein modifications in the cell, with manifold effects on the protein level as well as on the metabolome level. The acetyl group, donated by the metabolite acetyl-coenzyme A, can be co- or post-translationally attached to either the α-amino group of the N-terminus of proteins or to the ε-amino group of lysine residues. These reactions are catalyzed by various N-terminal and lysine acetyltransferases. In case of lysine acetylation, the reaction is enzymatically reversible via tightly regulated and metabolism-dependent mechanisms. The interplay between acetylation and deacetylation is crucial for many important cellular processes. In recent years, our understanding of protein acetylation has increased significantly by global proteomics analyses and in depth functional studies. This review gives a general overview of protein acetylation and the respective acetyltransferases, and focuses on the regulation of metabolic processes and physiological consequences that come along with protein acetylation.
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Affiliation(s)
- Adrian Drazic
- Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway
| | - Line M Myklebust
- Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway
| | - Rasmus Ree
- Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway; Department of Surgery, Haukeland University Hospital, N-5021 Bergen, Norway
| | - Thomas Arnesen
- Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway; Department of Surgery, Haukeland University Hospital, N-5021 Bergen, Norway.
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19
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Pratt MR, Abeywardana T, Marotta NP. Synthetic Proteins and Peptides for the Direct Interrogation of α-Synuclein Posttranslational Modifications. Biomolecules 2015; 5:1210-27. [PMID: 26120904 PMCID: PMC4598748 DOI: 10.3390/biom5031210] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/17/2015] [Accepted: 06/09/2015] [Indexed: 01/28/2023] Open
Abstract
α-Synuclein is the aggregation-prone protein associated with Parkinson’s disease (PD) and related neurodegenerative diseases. Complicating both its biological functions and toxic aggregation are a variety of posttranslational modifications. These modifications have the potential to either positively or negatively affect α-synuclein aggregation, raising the possibility that the enzymes that add or remove these modifications could be therapeutic targets in PD. Synthetic protein chemistry is uniquely positioned to generate site-specifically and homogeneously modified proteins for biochemical study. Here, we review the application of synthetic peptides and proteins towards understanding the effects of α-synuclein posttranslational modifications.
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Affiliation(s)
- Matthew R Pratt
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA.
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
| | | | - Nicholas P Marotta
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA.
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20
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Narkiewicz J, Giachin G, Legname G. In vitro aggregation assays for the characterization of α-synuclein prion-like properties. Prion 2015; 8:19-32. [PMID: 24552879 PMCID: PMC4116381 DOI: 10.4161/pri.28125] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Aggregation of α-synuclein plays a crucial role in the pathogenesis of synucleinopathies, a group of neurodegenerative diseases including Parkinson disease (PD), dementia with Lewy bodies (DLB), diffuse Lewy body disease (DLBD) and multiple system atrophy (MSA). The common feature of these diseases is a pathological deposition of protein aggregates, known as Lewy bodies (LBs) in the central nervous system. The major component of these aggregates is α-synuclein, a natively unfolded protein, which may undergo dramatic structural changes resulting in the formation of β-sheet rich assemblies. In vitro studies have shown that recombinant α-synuclein protein may polymerize into amyloidogenic fibrils resembling those found in LBs. These aggregates may be uptaken and propagated between cells in a prion-like manner. Here we present the mechanisms and kinetics of α-synuclein aggregation in vitro, as well as crucial factors affecting this process. We also describe how PD-linked α-synuclein mutations and some exogenous factors modulate in vitro aggregation. Furthermore, we present a current knowledge on the mechanisms by which extracellular aggregates may be internalized and propagated between cells, as well as the mechanisms of their toxicity.
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Smaldone G, Diana D, Pollegioni L, Di Gaetano S, Fattorusso R, Pedone E. Insight into conformational modification of alpha-synuclein in the presence of neuronal whole cells and of their isolated membranes. FEBS Lett 2015; 589:798-804. [DOI: 10.1016/j.febslet.2015.02.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 01/30/2015] [Accepted: 02/10/2015] [Indexed: 10/24/2022]
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22
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Protein Misfolding in Lipid-Mimetic Environments. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 855:33-66. [PMID: 26149925 DOI: 10.1007/978-3-319-17344-3_2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Among various cellular factors contributing to protein misfolding and subsequent aggregation, membranes occupy a special position due to the two-way relations between the aggregating proteins and cell membranes. On one hand, the unstable, toxic pre-fibrillar aggregates may interact with cell membranes, impairing their functions, altering ion distribution across the membranes, and possibly forming non-specific membrane pores. On the other hand, membranes, too, can modify structures of many proteins and affect the misfolding and aggregation of amyloidogenic proteins. The effects of membranes on protein structure and aggregation can be described in terms of the "membrane field" that takes into account both the negative electrostatic potential of the membrane surface and the local decrease in the dielectric constant. Water-alcohol (or other organic solvent) mixtures at moderately low pH are used as model systems to study the joint action of the local decrease of pH and dielectric constant near the membrane surface on the structure and aggregation of proteins. This chapter describes general mechanisms of structural changes of proteins in such model environments and provides examples of various proteins aggregating in the "membrane field" or in lipid-mimetic environments.
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23
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Molecular, Cellular, and Physiological Significance of N-Terminal Acetylation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 316:267-305. [DOI: 10.1016/bs.ircmb.2015.01.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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24
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N-alpha-acetylation of α-synuclein increases its helical folding propensity, GM1 binding specificity and resistance to aggregation. PLoS One 2014; 9:e103727. [PMID: 25075858 PMCID: PMC4116227 DOI: 10.1371/journal.pone.0103727] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/05/2014] [Indexed: 12/02/2022] Open
Abstract
A switch in the conformational properties of α-synuclein (αS) is hypothesized to be a key step in the pathogenic mechanism of Parkinson’s disease (PD). Whereas the beta-sheet-rich state of αS has long been associated with its pathological aggregation in PD, a partially alpha-helical state was found to be related to physiological lipid binding; this suggests a potential role of the alpha-helical state in controlling synaptic vesicle cycling and resistance to β-sheet rich aggregation. N-terminal acetylation is the predominant post-translational modification of mammalian αS. Using circular dichroism, isothermal titration calorimetry, and fluorescence spectroscopy, we have analyzed the effects of N-terminal acetylation on the propensity of recombinant human αS to form the two conformational states in interaction with lipid membranes. Small unilamellar vesicles of negatively charged lipids served as model membranes. Consistent with previous NMR studies using phosphatidylserine, we found that membrane-induced α-helical folding was enhanced by N-terminal acetylation and that greater exothermic heat could be measured upon vesicle binding of the modified protein. Interestingly, the folding and lipid binding enhancements with phosphatidylserine in vitro were weak when compared to that of αS with GM1, a lipid enriched in presynaptic membranes. The resultant increase in helical folding propensity of N-acetylated αS enhanced its resistance to aggregation. Our findings demonstrate the significance of the extreme N-terminus for folding nucleation, for relative GM1 specificity of αS-membrane interaction, and for a protective function of N-terminal-acetylation against αS aggregation mediated by GM1.
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25
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Lokappa SB, Suk JE, Balasubramanian A, Samanta S, Situ AJ, Ulmer TS. Sequence and Membrane Determinants of the Random Coil–Helix Transition of α-Synuclein. J Mol Biol 2014; 426:2130-44. [DOI: 10.1016/j.jmb.2014.02.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 02/24/2014] [Accepted: 02/28/2014] [Indexed: 11/16/2022]
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26
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Moriarty GM, Minetti CASA, Remeta DP, Baum J. A Revised Picture of the Cu(II)−α-Synuclein Complex: The Role of N-Terminal Acetylation. Biochemistry 2014; 53:2815-7. [DOI: 10.1021/bi5003025] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Gina M. Moriarty
- Department
of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Conceição A. S. A. Minetti
- Department
of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - David P. Remeta
- Department
of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Jean Baum
- Department
of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
- BioMaPS
Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854, United States
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27
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The many faces of proteins. FEBS Lett 2013; 587:995-6. [DOI: 10.1016/j.febslet.2013.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Alderson TR, Markley JL. Biophysical characterization of α-synuclein and its controversial structure. INTRINSICALLY DISORDERED PROTEINS 2013; 1:18-39. [PMID: 24634806 PMCID: PMC3908606 DOI: 10.4161/idp.26255] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 08/23/2013] [Indexed: 12/16/2022]
Abstract
α-synuclein, a presynaptic protein of poorly defined function, constitutes the main component of Parkinson disease-associated Lewy bodies. Extensive biophysical investigations have provided evidence that isolated α-synuclein is an intrinsically disordered protein (IDP) in vitro. Subsequently serving as a model IDP in numerous studies, α-synuclein has aided in the development of many technologies used to characterize IDPs and arguably represents the most thoroughly analyzed IDP to date. Recent reports, however, have challenged the disordered nature of α-synuclein inside cells and have instead proposed a physiologically relevant helical tetramer. Despite α-synuclein's rich biophysical history, a single coherent picture has not yet emerged concerning its in vivo structure, dynamics, and physiological role(s). We present herein a review of the biophysical discoveries, developments, and models pertinent to the characterization of α-synuclein's structure and analysis of the native tetramer controversy.
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Affiliation(s)
- T Reid Alderson
- Biochemistry Department; University of Wisconsin-Madison; Madison, WI USA
| | - John L Markley
- Biochemistry Department; University of Wisconsin-Madison; Madison, WI USA ; National Magnetic Resonance Facility at Madison; University of Wisconsin-Madison; Madison, WI USA
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