1
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Bhatt MR, Zondlo NJ. Electronic Control of Polyproline II Helix Stability via the Identity of Acyl Capping Groups: the Pivaloyl Group Particularly Promotes PPII. Chemistry 2024; 30:e202401454. [PMID: 38661017 DOI: 10.1002/chem.202401454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 04/24/2024] [Accepted: 04/25/2024] [Indexed: 04/26/2024]
Abstract
The type II polyproline helix (PPII) is a fundamental secondary structure of proteins, important in globular proteins, in intrinsically disordered proteins, and at protein-protein interfaces. PPII is stabilized in part by n→π* interactions between consecutive carbonyls, via electron delocalization between an electron-donor carbonyl lone pair (n) and an electron-acceptor carbonyl (π*) on the subsequent residue. We previously demonstrated that changes to the electronic properties of the acyl donor can predictably modulate the strength of n→π* interactions, with data from model compounds, in solution in chloroform, in the solid state, and computationally. Herein, we examined whether the electronic properties of acyl capping groups could modulate the stability of PPII in peptides in water. In X-PPGY-NH2 peptides (X=10 acyl capping groups), the effect of acyl group identity on PPII was quantified by circular dichroism and NMR spectroscopy. Electron-rich acyl groups promoted PPII relative to the standard acetyl (Ac-) group, with the pivaloyl and iso-butyryl groups most significantly increasing PPII. In contrast, acyl derivatives with electron-withdrawing substituents and the formyl group relatively disfavored PPII. Similar results, though lesser in magnitude, were also observed in X-APPGY-NH2 peptides, indicating that the capping group can impact PPII conformation at both proline and non-proline residues. The pivaloyl group was particularly favorable in promoting PPII. The effects of acyl capping groups were further analyzed in X-DfpPGY-NH2 and X-ADfpPGY-NH2 peptides, Dfp=4,4-difluoroproline. Data on these peptides indicated that acyl groups induced order Piv- > Ac- > For-. These results suggest that greater consideration should be given to the identity of acyl capping groups in inducing structure in peptides.
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Affiliation(s)
- Megh R Bhatt
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, United States
| | - Neal J Zondlo
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, United States
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2
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Liu S, Nguyen JB, Zhao Y, Schussler S, Kim S, Qiu H, Li N, Rosconi MP, Pyles EA. Development of a platform method for rapid detection and characterization of domain-specific post-translational modifications in bispecific antibodies. J Pharm Biomed Anal 2024; 244:116120. [PMID: 38547650 DOI: 10.1016/j.jpba.2024.116120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/14/2024] [Accepted: 03/17/2024] [Indexed: 04/29/2024]
Abstract
Charge heterogeneity is inherent to all therapeutic antibodies and arises from post-translational modifications (PTMs) and/or protein degradation events that may occur during manufacturing. Among therapeutic antibodies, the bispecific antibody (bsAb) containing two unique Fab arms directed against two different targets presents an additional layer of complexity to the charge profile. In the context of a bsAb, a single domain-specific PTM within one of the Fab domains may be sufficient to compromise target binding and could potentially impact the stability, safety, potency, and efficacy of the drug product. Therefore, characterization and routine monitoring of domain-specific modifications is critical to ensure the quality of therapeutic bispecific antibody products. We developed a Digestion-assisted imaged Capillary isoElectric focusing (DiCE) method to detect and quantitate domain-specific charge variants of therapeutic bispecific antibodies (bsAbs). The method involves enzymatic digestion using immunoglobulin G (IgG)-degrading enzyme of S. pyogenes (IdeS) to generate F(ab)2 and Fc fragments, followed by imaged capillary isoelectric focusing (icIEF) under reduced, denaturing conditions to separate the light chains (LCs) from the Fd domains. Our results suggest that DiCE is a highly sensitive method that is capable of quantitating domain-specific PTMs of a bsAb. In one case study, DiCE was used to quantitate unprocessed C-terminal lysine and site-specific glycation of Lys98 in the complementarity-determining region (CDR) of a bsAb that could not be accurately quantitated using conventional, platform-based charge variant analysis, such as intact icIEF. Quantitation of these PTMs by DiCE was comparable to results from peptide mapping, demonstrating that DiCE is a valuable orthogonal method for ensuring product quality. This method may also have potential applications for characterizing fusion proteins, antibody-drug conjugates, and co-formulated antibody cocktails.
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Affiliation(s)
- Sophia Liu
- Protein Biochemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Jennifer B Nguyen
- Protein Biochemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States.
| | - Yimeng Zhao
- Analytical Chemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Svetlana Schussler
- Preclinical Manufacturing and Process Development, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Sunnie Kim
- Analytical Chemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Haibo Qiu
- Analytical Chemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Ning Li
- Analytical Chemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Michael P Rosconi
- Protein Biochemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
| | - Erica A Pyles
- Protein Biochemistry, Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River Road, Tarrytown, NY 10591, United States
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3
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Rodríguez CS, Laurents DV. Architectonic principles of polyproline II helix bundle protein domains. Arch Biochem Biophys 2024; 756:109981. [PMID: 38593862 DOI: 10.1016/j.abb.2024.109981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/18/2024] [Accepted: 03/28/2024] [Indexed: 04/11/2024]
Abstract
Glycine rich polyproline II helix assemblies are an emerging class of natural domains found in several proteins with different functions and diverse origins. The distinct properties of these domains relative to those composed of α-helices and β-sheets could make glycine-rich polyproline II helix assemblies a useful building block for protein design. Whereas the high population of polyproline II conformers in disordered state ensembles could facilitate glycine-rich polyproline II helix folding, the architectonic bases of these structures are not well known. Here, we compare and analyze their structures to uncover common features. These protein domains are found to be highly tolerant of distinct flanking sequences. This speaks to the robustness of this fold and strongly suggests that glycine rich polyproline II assemblies could be grafted with other protein domains to engineer new structures and functions. These domains are also well packed with few or no cavities. Moreover, a significant trend towards antiparallel helix configuration is observed in all these domains and could provide stabilizing interactions among macrodipoles. Finally, extensive networks of Cα-H···OC hydrogen bonds are detected in these domains. Despite their diverse evolutionary origins and activities, glycine-rich polyproline II helix assemblies share architectonic features which could help design novel proteins.
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Affiliation(s)
| | - Douglas V Laurents
- Instituto de Química Física "Blas Cabrera" CSIC, Serrano 119 Madrid, Spain.
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4
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Ganguly HK, Ludwig BA, Tressler CM, Bhatt MR, Pandey AK, Quinn CM, Bai S, Yap GPA, Zondlo NJ. 4,4-Difluoroproline as a Unique 19F NMR Probe of Proline Conformation. Biochemistry 2024; 63:1131-1146. [PMID: 38598681 DOI: 10.1021/acs.biochem.3c00697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2024]
Abstract
Despite the importance of proline conformational equilibria (trans versus cis amide and exo versus endo ring pucker) on protein structure and function, there is a lack of convenient ways to probe proline conformation. 4,4-Difluoroproline (Dfp) was identified to be a sensitive 19F NMR-based probe of proline conformational biases and cis-trans isomerism. Within model compounds and disordered peptides, the diastereotopic fluorines of Dfp exhibit similar chemical shifts (ΔδFF = 0-3 ppm) when a trans X-Dfp amide bond is present. In contrast, the diastereotopic fluorines exhibit a large (ΔδFF = 5-12 ppm) difference in chemical shift in a cis X-Dfp prolyl amide bond. DFT calculations, X-ray crystallography, and solid-state NMR spectroscopy indicated that ΔδFF directly reports on the relative preference of one proline ring pucker over the other: a fluorine which is pseudo-axial (i.e., the pro-4R-F in an exo ring pucker, or the pro-4S-F in an endo ring pucker) is downfield, while a fluorine which is pseudo-equatorial (i.e., pro-4S-F when exo, or pro-4R-F when endo) is upfield. Thus, when a proline is disordered (a mixture of exo and endo ring puckers, as at trans-Pro in peptides in water), it exhibits a small Δδ. In contrast, when the Pro is ordered (i.e., when one ring pucker is strongly preferred, as in cis-Pro amide bonds, where the endo ring pucker is strongly favored), a large Δδ is observed. Dfp can be used to identify inherent induced order in peptides and to quantify proline cis-trans isomerism. Using Dfp, we discovered that the stable polyproline II helix (PPII) formed in the denatured state (8 M urea) exhibits essentially equal populations of the exo and endo proline ring puckers. In addition, the data with Dfp suggested the specific stabilization of PPII by water over other polar solvents. These data strongly support the importance of carbonyl solvation and n → π* interactions for the stabilization of PPII. Dfp was also employed to quantify proline cis-trans isomerism as a function of phosphorylation and the R406W mutation in peptides derived from the intrinsically disordered protein tau. Dfp is minimally sterically disruptive and can be incorporated in expressed proteins, suggesting its broad application in understanding proline cis-trans isomerization, protein folding, and local order in intrinsically disordered proteins.
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Affiliation(s)
- Himal K Ganguly
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Brice A Ludwig
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Caitlin M Tressler
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Megh R Bhatt
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Anil K Pandey
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Shi Bai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Glenn P A Yap
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Neal J Zondlo
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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Rajewski BH, Wright MM, Gerrein TA, Del Valle JR. N-Aminoglycine and Its Derivatives Stabilize PPII Secondary Structure. Org Lett 2023; 25:4366-4370. [PMID: 37276840 DOI: 10.1021/acs.orglett.3c01502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The identification of unnatural residues that stabilize polyproline type 2 (PPII) folds can aid in the design of peptidomimetics targeting PPII-binding domains. Here, we examine the impact of peptide backbone N-amination on PPII helix stability and find N-aminoglycine (aGly) to be an effective PPII promoter. Further derivatization of an aGly-containing peptide affords N'-alkylated analogues with increased helical propensity. Backbone N-amination of glycine represents a convenient approach to stabilize PPII conformation and allows for the diversity-oriented synthesis of optimally constrained folds.
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Affiliation(s)
- Benjamin H Rajewski
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Madison M Wright
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Taylor A Gerrein
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Juan R Del Valle
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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6
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Yarawsky AE, Ori AL, English LR, Whitten ST, Herr AB. Convergent behavior of extended stalk regions from staphylococcal surface proteins with widely divergent sequence patterns. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.06.523059. [PMID: 36711672 PMCID: PMC9881980 DOI: 10.1101/2023.01.06.523059] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Staphylococcus epidermidis and S. aureus are highly problematic bacteria in hospital settings. This stems, at least in part, from strong abilities to form biofilms on abiotic or biotic surfaces. Biofilms are well-organized multicellular aggregates of bacteria, which, when formed on indwelling medical devices, lead to infections that are difficult to treat. Cell wall-anchored (CWA) proteins are known to be important players in biofilm formation and infection. Many of these proteins have putative stalk-like regions or regions of low complexity near the cell wall-anchoring motif. Recent work demonstrated the strong propensity of the stalk region of the S. epidermidis accumulation-associated protein (Aap) to remain highly extended under solution conditions that typically induce compaction or other significant conformational changes. This behavior is consistent with the expected function of a stalk-like region that is covalently attached to the cell wall peptidoglycan and projects the adhesive domains of Aap away from the cell surface. In this study, we evaluate whether the ability to resist compaction is a common theme among stalk regions from various staphylococcal CWA proteins. Circular dichroism spectroscopy was used to examine secondary structure changes as a function of temperature and cosolvents along with sedimentation velocity analytical ultracentrifugation and SAXS to characterize structural characteristics in solution. All stalk regions tested are intrinsically disordered, lacking secondary structure beyond random coil and polyproline type II helix, and they all sample highly extended conformations. Remarkably, the Ser-Asp dipeptide repeat region of SdrC exhibited nearly identical behavior in solution when compared to the Aap Pro/Gly-rich region, despite highly divergent sequence patterns, indicating conservation of function by various distinct staphylococcal CWA protein stalk regions.
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Affiliation(s)
- Alexander E. Yarawsky
- Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Andrea L. Ori
- Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA,Medical Sciences Baccalaureate Program, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Lance R. English
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX 78666, USA
| | - Steven T. Whitten
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX 78666, USA
| | - Andrew B. Herr
- Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA,Division of Infectious Diseases, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
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7
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Haris L, Biehl R, Dulle M, Radulescu A, Holderer O, Hoffmann I, Stadler AM. Variation of Structural and Dynamical Flexibility of Myelin Basic Protein in Response to Guanidinium Chloride. Int J Mol Sci 2022; 23:ijms23136969. [PMID: 35805997 PMCID: PMC9266411 DOI: 10.3390/ijms23136969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/18/2022] [Accepted: 06/21/2022] [Indexed: 11/16/2022] Open
Abstract
Myelin basic protein (MBP) is intrinsically disordered in solution and is considered as a conformationally flexible biomacromolecule. Here, we present a study on perturbation of MBP structure and dynamics by the denaturant guanidinium chloride (GndCl) using small-angle scattering and neutron spin–echo spectroscopy (NSE). A concentration of 0.2 M GndCl causes charge screening in MBP resulting in a compact, but still disordered protein conformation, while GndCl concentrations above 1 M lead to structural expansion and swelling of MBP. NSE data of MBP were analyzed using the Zimm model with internal friction (ZIF) and normal mode (NM) analysis. A significant contribution of internal friction was found in compact states of MBP that approaches a non-vanishing internal friction relaxation time of approximately 40 ns at high GndCl concentrations. NM analysis demonstrates that the relaxation rates of internal modes of MBP remain unaffected by GndCl, while structural expansion due to GndCl results in increased amplitudes of internal motions. Within the model of the Brownian oscillator our observations can be rationalized by a loss of friction within the protein due to structural expansion. Our study highlights the intimate coupling of structural and dynamical plasticity of MBP, and its fundamental difference to the behavior of ideal polymers in solution.
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Affiliation(s)
- Luman Haris
- Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; (L.H.); (R.B.); (M.D.)
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | - Ralf Biehl
- Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; (L.H.); (R.B.); (M.D.)
| | - Martin Dulle
- Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; (L.H.); (R.B.); (M.D.)
| | - Aurel Radulescu
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungzentrum Jülich GmbH, 85747 Garching, Germany; (A.R.); (O.H.)
| | - Olaf Holderer
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungzentrum Jülich GmbH, 85747 Garching, Germany; (A.R.); (O.H.)
| | - Ingo Hoffmann
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, CEDEX 9, 38042 Grenoble, France;
| | - Andreas M. Stadler
- Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; (L.H.); (R.B.); (M.D.)
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
- Correspondence:
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8
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Zondlo NJ. Solvation stabilizes intercarbonyl n→π* interactions and polyproline II helix. Phys Chem Chem Phys 2022; 24:13571-13586. [PMID: 35635541 DOI: 10.1039/d2cp00857b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
n→π* interactions between consecutive carbonyls stabilize the α-helix and polyproline II helix (PPII) conformations in proteins. n→π* interactions have been suggested to provide significant conformational biases to the disordered states of proteins. To understand the roles of solvation on the strength of n→π* interactions, computational investigations were conducted on a model n→π* interaction, the twisted-parallel-offset formaldehyde dimer, as a function of explicit solvation of the donor and acceptor carbonyls, using water and HF. In addition, the effects of urea, thiourea, guanidinium, and monovalent cations on n→π* interaction strength were examined. Solvation of the acceptor carbonyl significantly strengthens the n→π* interaction, while solvation of the donor carbonyl only modestly weakens the n→π* interaction. The n→π* interaction strength was maximized with two solvent molecules on the acceptor carbonyl. Urea stabilized the n→π* interaction via simultaneous engagement of both oxygen lone pairs on the acceptor carbonyl. Solvent effects were further investigated in the model peptides Ac-Pro-NMe2, Ac-Ala-NMe2, and Ac-Pro2-NMe2. Solvent effects in peptides were similar to those in the formaldehyde dimer, with solvation of the acceptor carbonyl increasing n→π* interaction strength and resulting in more compact conformations, in both the proline endo and exo ring puckers, as well as a reduction in the energy difference between these ring puckers. Carbonyl solvation leads to an energetic preference for PPII over both the α-helix and β/extended conformations, consistent with experimental data that protic solvents and protein denaturants both promote PPII. Solvation of the acceptor carbonyl weakens the intraresidue C5 hydrogen bond that stabilizes the β conformation.
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Affiliation(s)
- Neal J Zondlo
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
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9
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Becht DC, Leavens MJ, Zeng B, Rothfuss MT, Briknarová K, Bowler BE. Residual Structure in the Denatured State of the Fast-Folding UBA(1) Domain from the Human DNA Excision Repair Protein HHR23A. Biochemistry 2022; 61:767-784. [PMID: 35430812 PMCID: PMC9150713 DOI: 10.1021/acs.biochem.2c00011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of the first ubiquitin-associated domain from HHR23A, UBA(1), was determined by X-ray crystallography at a 1.60 Å resolution, and its stability, folding kinetics, and residual structure under denaturing conditions have been investigated. The concentration dependence of thermal denaturation and size-exclusion chromatography indicate that UBA(1) is monomeric. Guanidine hydrochloride (GdnHCl) denaturation experiments reveal that the unfolding free energy, ΔGu°'(H2O), of UBA(1) is 2.4 kcal mol-1. Stopped-flow folding kinetics indicates sub-millisecond folding with only proline isomerization phases detectable at 25 °C. The full folding kinetics are observable at 4 °C, yielding a folding rate constant, kf, in the absence of a denaturant of 13,000 s-1 and a Tanford β-value of 0.80, consistent with a compact transition state. Evaluation of the secondary structure via circular dichroism shows that the residual helical structure in the denatured state is replaced by polyproline II structure as the GdnHCl concentration increases. Analysis of NMR secondary chemical shifts for backbone 15NH, 13CO, and 13Cα atoms between 4 and 7 M GdnHCl shows three islands of residual helical secondary structure that align in sequence with the three native-state helices. Extrapolation of the NMR data to 0 M GdnHCl demonstrates that helical structure would populate to 17-33% in the denatured state under folding conditions. Comparison with NMR data for a peptide corresponding to helix 1 indicates that this helix is stabilized by transient tertiary interactions in the denatured state of UBA(1). The high helical content in the denatured state, which is enhanced by transient tertiary interactions, suggests a diffusion-collision folding mechanism.
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Affiliation(s)
- Dustin C. Becht
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Moses J. Leavens
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Baisen Zeng
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Michael T. Rothfuss
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Klára Briknarová
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana 59812, United States
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10
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Ren C, Zheng Y, Liu C, Mencius J, Wu Z, Quan S. Molecular Characterization of an Intrinsically Disordered Chaperone Reveals Net-Charge Regulation in Chaperone Action. J Mol Biol 2021; 434:167405. [PMID: 34914967 DOI: 10.1016/j.jmb.2021.167405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 11/18/2022]
Abstract
Molecular chaperones are diverse biomacromolecules involved in the maintenance of cellular protein homeostasis (proteostasis). Here we demonstrate that in contrast to most chaperones with defined three-dimensional structures, the acid-inducible protein Asr in Escherichia coli is intrinsically disordered and exhibits varied aggregation-preventing or aggregation-promoting activities, acting as a "conditionally active chaperone". Bioinformatics and experimental analyses of Asr showed that it is devoid of hydrophobic patches but rich in positive charges and local polyproline II backbone structures. Asr contributes to the integrity of the bacterial outer membrane under mildly acidic conditions in vivo and possesses chaperone activities toward model clients in vitro. Notably, its chaperone activity is dependent on the net charges of clients: on the one hand, it inhibits the aggregation of clients with similar net charges; on the other hand, it stimulates the aggregation of clients with opposite net charges. Mutational analysis confirmed that positively charged residues in Asr are essential for the varied effects on protein aggregation, suggesting that electrostatic interactions are the major driving forces underlying Asr's proteostasis-related activity. These findings present a unique example of an intrinsically disordered molecular chaperone with distinctive dual functions-as an aggregase or as a chaperone-depending on the net charges of clients.
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Affiliation(s)
- Chang Ren
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China
| | - Yongxin Zheng
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China
| | - Chunlan Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China
| | - Jun Mencius
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China
| | - Zhili Wu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China
| | - Shu Quan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China; Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Shanghai 200237, China.
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11
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Phosphorylation of TIP3 Aquaporins during Phaseolus vulgaris Embryo Development. Cells 2019; 8:cells8111362. [PMID: 31683651 PMCID: PMC6912600 DOI: 10.3390/cells8111362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 11/19/2022] Open
Abstract
The membrane phosphoproteome in plant seed changes dynamically during embryo development. We examined the patterns of Phaseolus vulgaris (common bean) seed membrane protein phosphorylation from the mid-maturation stage until two days after germination. Serine and threonine phosphorylation declined during seed maturation while tyrosine phosphorylation remained relatively constant. We discovered that the aquaporin PvTIP3;1 is the primary seed membrane phosphoprotein, and PvTIP3;2 shows a very low level of expression. The level of phosphorylated Ser7 in PvTIP3;1 increased four-fold after seed maturation. Since phosphorylation increases water channel activity, we infer that water transport by PvTIP3;1 is highest in dry and germinating seeds, which would be optimal for seed imbibition. By the use of isoform-specific, polyclonal peptide antibodies, we found that PvTIP3;2 is expressed in a developmental pattern similar to PvTIP3;1. Unexpectedly, PvTIP3;2 is tyrosine phosphorylated following seed maturation, which may suggest a mechanism for the regulation of PvTIP3;2 following seed germination. Analysis of protein secondary structure by circular dichroism spectroscopy indicated that the amino-terminal domain of PvTIP3;1 is generally unstructured, and phosphorylation increases polyproline II (PPII) helical structure. The carboxy-terminal domain also gains PPII character, but in a pH-dependent manner. These structural changes are a first step to understand TIP3 aquaporin regulation.
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Więch A, Rowińska-Żyrek M, Wątły J, Czarnota A, Hołubowicz R, Szewczuk Z, Ożyhar A, Orłowski M. The intrinsically disordered C-terminal F domain of the ecdysteroid receptor from Aedes aegypti exhibits metal ion-binding ability. J Steroid Biochem Mol Biol 2019; 186:42-55. [PMID: 30243841 DOI: 10.1016/j.jsbmb.2018.09.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/29/2018] [Accepted: 09/12/2018] [Indexed: 11/18/2022]
Abstract
The dominant vector of dengue and Zika diseases is a female Aedes aegypti mosquito. Its reproduction is controlled by the formation of an active heterodimer complex of the 20-hydroxyecdysone receptor (EcR) and Ultraspiracle protein (Usp). Although EcR exhibits a structural and functional organization typical of nuclear receptors (NRs), the EcR C-terminus has an additional F domain (AaFEcR) that is rarely present in the NRs superfamily. The presence of F domains is evolutionarily not well conserved in the NRs. The structure-function relationship of EcR F domains in arthropods is unclear and enigmatic. To date, there have been no data concerning the structure and function of AaFEcR. Our results showed that AaFEcR belongs to a family of intrinsically disordered proteins (IDPs) and possesses putative pre-molten globule (PMG) characteristics. Unexpectedly, additional amino acid composition in silico analyses revealed the presence of short unique repeated Pro-His clusters forming an HGPHPHPHG motif, which is similar to those responsible for Zn2+ and Cu2+ binding in histidine-proline-rich glycoproteins (HPRGs). Using SEC, SV-AUC and ESI-TOF MS, we showed that the intrinsically disordered AaFEcR is able to bind metal ions and form complexes with these ions. Our studies provide new insight into the structural organization and activities of the F domains of NRs. This unique for the F domains of NRs ion-binding propensity demonstrated by the AaFEcR domain may be a part of the ecdysteroid receptor's mechanism for regulating the expression of genes encoding oxidative stress-protecting proteins.
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Affiliation(s)
- Anna Więch
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | | | - Joanna Wątły
- Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland
| | - Aleksandra Czarnota
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Rafał Hołubowicz
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | | | - Andrzej Ożyhar
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Marek Orłowski
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland.
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Wetzler DE, Fuchs Wightman F, Bucci HA, Rinaldi J, Caramelo JJ, Iusem ND, Ricardi MM. Conformational plasticity of the intrinsically disordered protein ASR1 modulates its function as a drought stress-responsive gene. PLoS One 2018; 13:e0202808. [PMID: 30138481 PMCID: PMC6107238 DOI: 10.1371/journal.pone.0202808] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 08/09/2018] [Indexed: 11/18/2022] Open
Abstract
Plants in arid zones are constantly exposed to drought stress. The ASR protein family (Abscisic, Stress, Ripening) -a subgroup of the late embryogenesis abundant superfamily- is involved in the water stress response and adaptation to dry environments. Tomato ASR1, as well as other members of this family, is an intrinsically disordered protein (IDP) that functions as a transcription factor and a chaperone. Here we employed different biophysical techniques to perform a deep in vitro characterization of ASR1 as an IDP and showed how both environmental factors and in vivo targets modulate its folding. We report that ASR1 adopts different conformations such as α-helix or polyproline type II in response to environmental changes. Low temperatures and low pH promote the polyproline type II conformation (PII). While NaCl increases PII content and slightly destabilizes α-helix conformation, PEG and glycerol have an important stabilizing effect of α-helix conformation. The binding of Zn2+in the low micromolar range promotes α-helix folding, while extra Zn2+ results in homo-dimerization. The ASR1-DNA binding is sequence specific and dependent on Zn2+. ASR1 chaperone activity does not change upon the structure induction triggered by the addition of Zn2+. Furthermore, trehalose, which has no effect on the ASR1 structure by itself, showed a synergistic effect on the ASR1-driven heat shock protection towards the reporter enzyme citrate synthase (CS). These observations prompted the development of a FRET reporter to sense ASR1 folding in vivo. Its performance was confirmed in Escherichia coli under saline and osmotic stress conditions, representing a promising probe to be used in plant cells. Overall, this work supports the notion that ASR1 plasticity is a key feature that facilitates its response to drought stress and its interaction with specific targets.
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Affiliation(s)
- Diana E. Wetzler
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail: (DW); (MR)
| | - Federico Fuchs Wightman
- Departamento de Fisiología y Biología Molecular y Celular (FBMC), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Hernan A. Bucci
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Jimena Rinaldi
- Fundación Instituto Leloir, Buenos Aires, Argentina e Instituto de investigaciones Bioquímicas de Buenos Aires (IIBBA- CONICET), Buenos Aires, Argentina
| | - Julio J. Caramelo
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Fundación Instituto Leloir, Buenos Aires, Argentina e Instituto de investigaciones Bioquímicas de Buenos Aires (IIBBA- CONICET), Buenos Aires, Argentina
| | - Norberto D. Iusem
- Departamento de Fisiología y Biología Molecular y Celular (FBMC), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Martiniano M. Ricardi
- Departamento de Fisiología y Biología Molecular y Celular (FBMC), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail: (DW); (MR)
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14
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Lella M, Mahalakshmi R. Solvation driven conformational transitions in the second transmembrane domain of mycobacteriophage holin. Biopolymers 2017; 108. [DOI: 10.1002/bip.22894] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 05/11/2016] [Accepted: 05/31/2016] [Indexed: 12/29/2022]
Affiliation(s)
- Muralikrishna Lella
- Molecular Biophysics Laboratory, Department of Biological Sciences; Indian Institute of Science Education and Research; Bhopal 462023 India
| | - Radhakrishnan Mahalakshmi
- Molecular Biophysics Laboratory, Department of Biological Sciences; Indian Institute of Science Education and Research; Bhopal 462023 India
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15
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Chin AF, Toptygin D, Elam WA, Schrank TP, Hilser VJ. Phosphorylation Increases Persistence Length and End-to-End Distance of a Segment of Tau Protein. Biophys J 2016; 110:362-371. [PMID: 26789759 DOI: 10.1016/j.bpj.2015.12.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 11/24/2015] [Accepted: 12/07/2015] [Indexed: 11/30/2022] Open
Abstract
Intrinsically disordered regions of proteins, which lack unique tertiary structure under physiological conditions, are enriched in phosphorylation sites and in significant local bias toward the polyproline II conformation. The overrepresented coincidence of this posttranslational regulatory signal and local conformational bias within unstructured regions raises a question: can phosphorylation serve to manipulate the conformational preferences of a disordered protein? In this study, we use time-resolved fluorescence resonance energy transfer and a, to our knowledge, novel data analysis method to directly measure the end-to-end distance distribution of a phosphorylatable peptide derived from the human microtubule associated protein tau. Our results show that phosphorylation at threonine or serine extends the end-to-end distance and increases the effective persistence length of the tested model peptides. Unexpectedly, the extension is independent of salt concentration, suggestive of a nonelectrostatic origin. The phosphorylation extension and stiffening effect provides a peptide-scale physical interpretation for the posttranslational regulation of the highly abundant protein-protein interactions found in disordered proteins, as well as a potential insight into the regulatory mechanism of the tau protein's microtubule binding activity.
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Affiliation(s)
- Alexander F Chin
- Department of Biology, Johns Hopkins University, Baltimore, Maryland
| | - Dmitri Toptygin
- Department of Biology, Johns Hopkins University, Baltimore, Maryland
| | - W Austin Elam
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Travis P Schrank
- Department of Otolaryngology, Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina
| | - Vincent J Hilser
- Department of Biology, Johns Hopkins University, Baltimore, Maryland; T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland.
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16
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Molinas MF, Benavides L, Castro MA, Murgida DH. Stability, redox parameters and electrocatalytic activity of a cytochrome domain from a new subfamily. Bioelectrochemistry 2015; 105:25-33. [DOI: 10.1016/j.bioelechem.2015.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 04/21/2015] [Accepted: 05/03/2015] [Indexed: 11/24/2022]
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17
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Wu D, Du X, Shi J, Zhou J, Xu B. Supramolecular Nanofibers/Hydrogels of the Conjugates of Nucleobase, Saccharide, and Amino Acids. CHINESE J CHEM 2014. [DOI: 10.1002/cjoc.201400092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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18
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Bilayer surface association of the pHLIP peptide promotes extensive backbone desolvation and helically-constrained structures. Biophys Chem 2014; 187-188:1-6. [DOI: 10.1016/j.bpc.2013.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 11/15/2013] [Accepted: 12/15/2013] [Indexed: 01/23/2023]
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19
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Transition state and ground state properties of the helix-coil transition in peptides deduced from high-pressure studies. Proc Natl Acad Sci U S A 2013; 110:20988-93. [PMID: 24324160 DOI: 10.1073/pnas.1317973110] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Volume changes associated with protein folding reactions contain valuable information about the folding mechanism and the nature of the transition state. However, meaningful interpretation of such data requires that overall volume changes be deconvoluted into individual contributions from different structural components. Here we focus on one type of structural element, the α-helix, and measure triplet-triplet energy transfer at high pressure to determine volume changes associated with the helix-coil transition. Our results reveal that the volume of a 21-amino-acid alanine-based peptide shrinks upon helix formation. Thus, helices, in contrast with native proteins, become more stable with increasing pressure, explaining the frequently observed helical structures in pressure-unfolded proteins. Both helix folding and unfolding become slower with increasing pressure. The volume changes associated with the addition of a single helical residue to a preexisting helix were obtained by comparing the experimental results with Monte Carlo simulations based on a kinetic linear Ising model. The reaction volume for adding a single residue to a helix is small and negative (-0.23 cm(3) per mol = -0.38 Å(3) per molecule) implying that intrahelical hydrogen bonds have a smaller volume than peptide-water hydrogen bonds. In contrast, the transition state has a larger volume than either the helical or the coil state, with activation volumes of 2.2 cm(3)/mol (3.7 Å(3) per molecule) for adding and 2.4 cm(3)/mol (4.0 Å(3) per molecule) for removing one residue. Thus, addition or removal of a helical residue proceeds through a transitory high-energy state with a large volume, possibly due to the presence of unsatisfied hydrogen bonds, although steric effects may also contribute.
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20
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21
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Hack V, Reuter C, Opitz R, Schmieder P, Beyermann M, Neudörfl JM, Kühne R, Schmalz HG. Efficient α-Helix Induction in a Linear Peptide Chain byN-Capping with a Bridged-tricyclic Diproline Analogue. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Hack V, Reuter C, Opitz R, Schmieder P, Beyermann M, Neudörfl JM, Kühne R, Schmalz HG. Efficient α-Helix Induction in a Linear Peptide Chain byN-Capping with a Bridged-tricyclic Diproline Analogue. Angew Chem Int Ed Engl 2013; 52:9539-43. [DOI: 10.1002/anie.201302014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Revised: 04/11/2013] [Indexed: 11/11/2022]
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23
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Elam WA, Schrank TP, Campagnolo AJ, Hilser VJ. Evolutionary conservation of the polyproline II conformation surrounding intrinsically disordered phosphorylation sites. Protein Sci 2013; 22:405-17. [PMID: 23341186 DOI: 10.1002/pro.2217] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 11/06/2022]
Abstract
Intrinsically disordered (ID) proteins function in the absence of a unique stable structure and appear to challenge the classic structure-function paradigm. The extent to which ID proteins take advantage of subtle conformational biases to perform functions, and whether signals for such mechanism can be identified in proteome-wide studies is not well understood. Of particular interest is the polyproline II (PII) conformation, suggested to be highly populated in unfolded proteins. We experimentally determine a complete calorimetric propensity scale for the PII conformation. Projection of the scale into representative eukaryotic proteomes reveals significant PII bias in regions coding for ID proteins. Importantly, enrichment of PII in ID proteins, or protein segments, is also captured by other PII scales, indicating that this enrichment is robustly encoded and universally detectable regardless of the method of PII propensity determination. Gene ontology (GO) terms obtained using our PII scale and other scales demonstrate a consensus for molecular functions performed by high PII proteins across the proteome. Perhaps the most striking result of the GO analysis is conserved enrichment (P < 10(-8) ) of phosphorylation sites in high PII regions found by all PII scales. Subsequent conformational analysis reveals a phosphorylation-dependent modulation of PII, suggestive of a conserved "tunability" within these regions. In summary, the application of an experimentally determined polyproline II (PII) propensity scale to proteome-wide sequence analysis and gene ontology reveals an enrichment of PII bias near disordered phosphorylation sites that is conserved throughout eukaryotes.
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Affiliation(s)
- W Austin Elam
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
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24
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Elam WA, Schrank TP, Campagnolo AJ, Hilser VJ. Temperature and urea have opposing impacts on polyproline II conformational bias. Biochemistry 2013; 52:949-58. [PMID: 23350874 DOI: 10.1021/bi301435p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The native states of globular proteins have been accessed in atomic detail by X-ray crystallography and nuclear magnetic resonance spectroscopy, yet characterization of denatured proteins beyond global metrics has proven to be elusive. Denatured proteins have been observed to exhibit global geometric properties of a random coil polymer. However, this does not preclude the existence of nonrandom, local conformational bias that may be significant for protein folding and function. Indeed, circular dichroism (CD) spectroscopy and other methods have suggested that the denatured state contains considerable local bias to the polyproline II (PII) conformation. Here, we develop predictive models to determine the extent that temperature and the chemical denaturant urea modulate PII propensity. In agreement with our predictive model, PII propensity is observed experimentally to decrease with an increase in temperature. Conversely, urea appears to promote the PII conformation as determined by CD and isothermal titration calorimetry. Importantly, the calorimetric data are in quantitative agreement with a model that predicts the stability of the PII helix relative to other denatured state conformations based upon solvent accessible surface area and experimentally measured Gibbs transfer free energies. The ability of urea to promote the PII conformation can be attributed to the favorable interaction of urea with the peptide backbone. Thus, perturbing denatured states by temperature or cosolutes has subtle, yet opposing, impacts on local PII conformational biases. These results have implications for protein folding as well as for the function of signaling proteins that bind proline-rich targets in globular or intrinsically disordered proteins.
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Affiliation(s)
- W Austin Elam
- T. C. Jenkins Department of Biophysics and Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, United States
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25
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Scaling properties of glycine-rich sequences in guanidine hydrochloride solutions. Biophys J 2012; 102:1969-78. [PMID: 22768954 DOI: 10.1016/j.bpj.2012.03.049] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 03/20/2012] [Accepted: 03/22/2012] [Indexed: 11/23/2022] Open
Abstract
The intrinsic polymer properties of glycine-rich sequences are evaluated with a set of iso-1-cytochrome c variants with N-terminal inserts of the sequence (GGGGGK)(n) for n = 1-5. The thermodynamics and kinetics of His-heme loop formation are measured as a function of guanidine hydrochloride (GdnHCl) concentration for loop sizes ranging from 22 to 46 residues. The scaling exponent for loop formation, ν(3), evaluated using the Jacobson-Stockmayer equation is near 1.8, at 1.5 and 3.0 M GdnHCl, but it increases to 2.2 in 6.0 M GdnHCl. Previous work on a set of iso-1-cytochrome c variants with (AAAAAK)(n) inserts gave ν(3) = 2.2 for alanine-rich sequences in both 3.0 and 6.0 M GdnHCl. Chain stiffness was evaluated from the relative magnitude of Flory's characteristic ratio, C(n), for alanine-rich versus glycine-rich sequences. In 3.0 M GdnHCl, C(n)(Ala)/C(n)(Gly) is 1.6, decreasing to 1.3 in 6.0 M GdnHCl. The data suggest that solvent-backbone interactions dominate polypeptide conformational properties under good solvent conditions whereas side-chain-dependent properties are more important under poor solvent conditions. The results provide a direct experimental assessment in terms of polymer properties of the distinct roles of Gly versus Ala in the folding code.
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26
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Mirkin NG, Krimm S. Water interaction differences determine the relative energetic stability of the polyproline II conformation of the alanine dipeptide in aqueous environments. Biopolymers 2012; 97:789-94. [DOI: 10.1002/bip.22064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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27
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Crevenna A, Naredi-Rainer N, Lamb D, Wedlich-Söldner R, Dzubiella J. Effects of Hofmeister ions on the α-helical structure of proteins. Biophys J 2012; 102:907-15. [PMID: 22385862 PMCID: PMC3283803 DOI: 10.1016/j.bpj.2012.01.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/15/2011] [Accepted: 01/11/2012] [Indexed: 01/20/2023] Open
Abstract
The molecular conformation of proteins is sensitive to the nature of the aqueous environment. In particular, the presence of ions can stabilize or destabilize (denature) protein secondary structure. The underlying mechanisms of these actions are still not fully understood. Here, we combine circular dichroism (CD), single-molecule Förster resonance energy transfer, and atomistic computer simulations to elucidate salt-specific effects on the structure of three peptides with large α-helical propensity. CD indicates a complex ion-specific destabilization of the α-helix that can be rationalized by using a single salt-free computer simulation in combination with the recently introduced scheme of ion-partitioning between nonpolar and polar peptide surfaces. Simulations including salt provide a molecular underpinning of this partitioning concept. Furthermore, our single-molecule Förster resonance energy transfer measurements reveal highly compressed peptide conformations in molar concentrations of NaClO(4) in contrast to strong swelling in the presence of GdmCl. The compacted states observed in the presence of NaClO(4) originate from a tight ion-backbone network that leads to a highly heterogeneous secondary structure distribution and an overall lower α-helical content that would be estimated from CD. Thus, NaClO(4) denatures by inducing a molten globule-like structure that seems completely off-pathway between a fully folded helix and a coil state.
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Affiliation(s)
- Alvaro H. Crevenna
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Nikolaus Naredi-Rainer
- Physical Chemistry, Department for Chemistry and Biochemistry and Center for Nano Science (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
- Center for Integrated Protein Science Munich, Munich, Germany
| | - Don C. Lamb
- Physical Chemistry, Department for Chemistry and Biochemistry and Center for Nano Science (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
- Center for Integrated Protein Science Munich, Munich, Germany
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Roland Wedlich-Söldner
- Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Joachim Dzubiella
- Physics Department T37, Technische Universität München, Garching, Germany
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Berlin, Germany
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
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28
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Chemes LB, Alonso LG, Noval MG, de Prat-Gay G. Circular dichroism techniques for the analysis of intrinsically disordered proteins and domains. Methods Mol Biol 2012; 895:387-404. [PMID: 22760329 DOI: 10.1007/978-1-61779-927-3_22] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Circular dichroism (CD) spectroscopy is a simple and powerful technique, which allows for the assessment of the conformational properties of a protein or protein domain. Intrinsically disordered proteins (IDPs), as discussed throughout this series, differ from random coil polypeptides in that different regions present specific conformational preferences, exhibiting dynamic secondary structure content [1]. These dynamic secondary structure elements can be stabilized or perturbed by different chemical (solvent, ionic strength, pH) or physical (temperature) agents, by posttranslational modifications, and by ligands. This information is important for defining ID nature. As IDPs present dynamic conformations, circular dichroism measurements (and other approaches as well) should be carried out not as single spectra performed in unique conditions, but instead changing the chemical conditions and observing the behavior, as part of the determination of the ID nature.In this chapter, we present the basic methodology for performing Far-UV CD measurements on a protein of interest and for identifying and characterizing intrinsically disordered regions, and several protocols for the analysis of residual secondary structure present in the protein under study. These techniques are straightforward to perform; they require minimal training and can be preliminary to more complex methodologies such as NMR.
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Affiliation(s)
- Lucía B Chemes
- Protein Structure, Function and Engineering Laboratory, Fundación Instituto Leloir and Instituto de Investigaciones Bioquímicas, Buenos Aires, Argentina.
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29
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Wang M, JiJi RD. Resolution of localized small molecule–Aβ interactions by deep-ultraviolet resonance Raman spectroscopy. Biophys Chem 2011; 158:96-103. [DOI: 10.1016/j.bpc.2011.05.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 05/19/2011] [Accepted: 05/19/2011] [Indexed: 01/13/2023]
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30
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Moradi M, Babin V, Sagui C, Roland C. PPII propensity of multiple-guest amino acids in a proline-rich environment. J Phys Chem B 2011; 115:8645-56. [PMID: 21630640 DOI: 10.1021/jp203874f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
There has been considerable debate about the intrinsic PPII propensity of amino acid residues in denatured polypeptides. Experimentally, this scale is based on the behavior of guest amino acid residues placed in the middle of proline-based hosts. We have used classical molecular dynamics simulations combined with replica-exchange methods to carry out a comprehensive analysis of the conformational equilibria of proline-based host oligopeptides with multiple guest amino acids including alanine, glutamine, valine, and asparagine. The tracked structural characteristics include the secondary structural motifs based on the Ramachandran angles and the cis/trans isomerization of the prolyl bonds. In agreement with our recent study of single amino acid guests, we did not observe an intrinsic PPII propensity in any of the guest amino acids in a multiple-guest setting. Instead, the experimental results can be explained in terms of (i) the steric restrictions imposed on the C-terminal guest amino acid that is immediately followed by a proline residue and (ii) an increase in the trans content of the prolyl bonds due to the presence of guest residues. In terms of the latter, we found that the more guests added to the system, the larger the increase in the trans content of the prolyl bonds, which results in an effective increase in the PPII content of the peptide.
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Affiliation(s)
- Mahmoud Moradi
- Center for High Performance Simulations (CHiPS) and Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202, United States
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Nagel L, Plattner C, Budke C, Majer Z, DeVries AL, Berkemeier T, Koop T, Sewald N. Synthesis and characterization of natural and modified antifreeze glycopeptides: glycosylated foldamers. Amino Acids 2011; 41:719-32. [DOI: 10.1007/s00726-011-0937-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 04/18/2011] [Indexed: 11/29/2022]
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32
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Moradi M, Babin V, Sagui C, Roland C. A statistical analysis of the PPII propensity of amino acid guests in proline-rich peptides. Biophys J 2011; 100:1083-93. [PMID: 21320454 DOI: 10.1016/j.bpj.2010.12.3742] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/06/2010] [Accepted: 12/27/2010] [Indexed: 12/29/2022] Open
Abstract
There has been considerable debate about the intrinsic PPII propensity of amino-acid residues in denatured polypeptides. Experimentally, the propensity scale is based on the behavior of guest amino-acid residues placed in the middle of polyproline hosts. We have used classical molecular dynamics simulations, with state-of-the-art force fields to carry out a comprehensive analysis of the conformational equilibria of the proline-based host oligopeptides with single guests. The tracked structural characteristics include the PPII content, the cis/trans isomerization of the prolyl bonds, the puckering of the pyrrolidine rings of the proline residues, and the secondary structural motifs. We find no evidence for an intrinsic PPII propensity in any of the guest amino acids other than proline. Instead, the PPII content as derived from experiments may be explained in terms of: 1), a local correlation between the dihedral angles of the guest amino acid and the proline residue immediately preceding it; and 2), a nonlocal correlation between the cis/trans states of the peptide bonds. In terms of the latter, we find that the presence of a guest (other than proline, tyrosine, or tryptophan) increases the trans content of most of the prolyl bonds, which results in an effective increase of the peptide PPII content. With respect to the local dihedral correlations, we find that these are well described in terms of the so-called odds-ratio statistic. Expressed in terms of free energy language, the PPII content based on the odds-ratio of the relevant residues correlate well with the experimentally measured PPII content.
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Affiliation(s)
- Mahmoud Moradi
- Center for High Performance Simulations (CHiPS) and Department of Physics, North Carolina State University, Raleigh, North Carolina, USA
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33
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Abstract
The susceptibility of monoclonal antibodies (mAbs) to undergo cold denaturation remains unexplored. In this study, the phenomenon of cold denaturation was investigated for a mAb, mAb1, through thermodynamic and spectroscopic analyses. Tryptophan fluorescence and circular dichroism (CD) spectra were recorded for the guanidine hydrochloride (GuHCl)-induced unfolding of mAb1 at pH 6.3 at temperatures ranging from -5 to 50 degrees C. A three-state unfolding model incorporating the linear extrapolation method was fit to the fluorescence data to obtain an apparent free energy of unfolding, DeltaG(u), at each temperature. CD studies revealed that mAb1 exhibited polyproline II helical structure at low temperatures and at high GuHCl concentrations. The Gibbs-Helmholtz expression fit to the DeltaG(u) versus temperature data from fluorescence gave a DeltaC(p) of 8.0 kcal mol(-1) K(-1), a maximum apparent stability of 23.7 kcal mol(-1) at 18 degrees C, and an apparent cold denaturation temperature (T(CD)) of -23 degrees C. DeltaG(u) values for another mAb (mAb2) with a similar framework exhibited less stability at low temperatures, suggesting a depressed protein stability curve and a higher relative T(CD). Direct experimental evidence of the susceptibility of mAb1 and mAb2 to undergo cold denaturation in the absence of denaturant was confirmed at pH 2.5. Thus, mAbs have a potential to undergo cold denaturation at storage temperatures near -20 degrees C (pH 6.3), and this potential needs to be evaluated independently for individual mAbs.
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Affiliation(s)
- Kristi L Lazar
- Early Stage Pharmaceutical Development, Genentech, Inc., San Francisco, CA, USA
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Maheshwari R, Levenson EA, Kiick KL. Manipulation of electrostatic and saccharide linker interactions in the design of efficient glycopolypeptide-based cholera toxin inhibitors. Macromol Biosci 2010; 10:68-81. [PMID: 19780061 PMCID: PMC2893567 DOI: 10.1002/mabi.200900182] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Multivalent, glycopolymer inhibitors designed for the treatment of disease and pathogen infection have shown improvements in binding correlated with general changes in glycopolymer architecture and composition. We have previously demonstrated that control of glycopolypeptide backbone extension and ligand spacing significantly impacts the inhibition of the cholera toxin B subunit pentamer (CT B(5)) by these polymers. In the studies reported here, we elucidate the role of backbone charge and linker length in modulating the inhibition event. Peptides of the sequence AXPXG (where X is a positive, neutral or negative amino acid), equipped with the alkyne functionality of propargyl glycine, were designed and synthesized via solid-phase peptide synthetic methods and glycosylated via Cu(I)-catalyzed alkyne-azide cycloaddition reactions. The capacity of the glycopeptides to inhibit the binding of the B(5) subunit of cholera toxin was evaluated. These studies indicated that glycopeptides with a negatively charged backbone show improved inhibition of the binding event relative to the other glycopeptides. In addition, variations in the length of the linker between the peptide and the saccharide ligand also affected the inhibition of CT by the glycopeptides. Our findings suggest that, apart from appropriate saccharide spacing and polypeptide chain extension, saccharide linker conformation and the systematic placement of charges on the polypeptide backbone are also significant variables that can be tuned to improve the inhibitory potencies of glycopolypeptide-based multivalent inhibitors.
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Affiliation(s)
- Ronak Maheshwari
- Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716 USA Fax: +1 (302) 831-4545
| | - Eric A. Levenson
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 USA
| | - Kristi L. Kiick
- Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716 USA Fax: +1 (302) 831-4545. Delaware Biotechnology Institute, 15 Innovation Way, Newark, Delaware 19711 USA
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35
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Hu KN, Havlin RH, Yau WM, Tycko R. Quantitative determination of site-specific conformational distributions in an unfolded protein by solid-state nuclear magnetic resonance. J Mol Biol 2009; 392:1055-73. [PMID: 19647001 DOI: 10.1016/j.jmb.2009.07.073] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 06/27/2009] [Accepted: 07/25/2009] [Indexed: 10/20/2022]
Abstract
Solid-state nuclear magnetic resonance (NMR) techniques are used to investigate the structure of the 35-residue villin headpiece subdomain (HP35) in folded, partially denatured, and fully denatured states. Experiments are carried out in frozen glycerol/water solutions, with chemical denaturation by guanidine hydrochloride (GdnHCl). Without GdnHCl, two-dimensional solid-state (13)C NMR spectra of samples prepared with uniform (13)C labeling of selected residues show relatively sharp cross-peaks at chemical shifts that are consistent with the known three-helix bundle structure of folded HP35. At high GdnHCl concentrations, most cross-peaks broaden and shift, qualitatively indicating disruption of the folded structure and development of static conformational disorder in the frozen denatured state. Conformational distributions at one residue in each helical segment are probed quantitatively with three solid-state NMR techniques that provide independent constraints on backbone varphi and psi torsion angles in samples with sequential pairs of carbonyl (13)C labels. Without GdnHCl, the combined data are well fit by alpha-helical conformations. At [GdnHCl]=4.5 M, corresponding to the approximate denaturation midpoint, the combined data are well fit by a combination of alpha-helical and partially extended conformations at each site, but with a site-dependent population ratio. At [GdnHCl]=7.0 M, corresponding to the fully denatured state, the combined data are well fit by a combination of partially extended and polyproline II conformations, again with a site-dependent population ratio. Two entirely different models for conformational distributions lead to nearly the same best-fit distributions, demonstrating the robustness of these conclusions. This work represents the first quantitative investigation of site-specific conformational distributions in partially folded and unfolded states of a protein by solid-state NMR.
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Affiliation(s)
- Kan-Nian Hu
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 5, Room 112, Bethesda, MD 20892-0520, USA
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36
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Wetzler DE, Gallo M, Melis R, Eliseo T, Nadra AD, Ferreiro DU, Paci M, Sánchez IE, Cicero DO, de Prat Gay G. A strained DNA binding helix is conserved for site recognition, folding nucleation, and conformational modulation. Biopolymers 2009; 91:432-43. [PMID: 19156829 DOI: 10.1002/bip.21146] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nucleic acid recognition is often mediated by alpha-helices or disordered regions that fold into alpha-helix on binding. A peptide bearing the DNA recognition helix of HPV16 E2 displays type II polyproline (PII) structure as judged by pH, temperature, and solvent effects on the CD spectra. NMR experiments indicate that the canonical alpha-helix is stabilized at the N-terminus, while the PII forms at the C-terminus half of the peptide. Re-examination of the dihedral angles of the DNA binding helix in the crystal structure and analysis of the NMR chemical shift indexes confirm that the N-terminus half is a canonical alpha-helix, while the C-terminal half adopts a 3(10) helix structure. These regions precisely match two locally driven folding nucleii, which partake in the native hydrophobic core and modulate a conformational switch in the DNA binding helix. The peptide shows only weak and unspecific residual DNA binding, 10(4)-fold lower affinity, and 500-fold lower discrimination capacity compared with the domain. Thus, the precise side chain conformation required for modulated and tight physiological binding by HPV E2 is largely determined by the noncanonical strained alpha-helix conformation, "presented" by this unique architecture. (c) 2009 Wiley Periodicals, Inc. Biopolymers 91: 432-443, 2009.
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Affiliation(s)
- Diana E Wetzler
- Fundación Instituto Leloir and IIBBA-CONICET, Patricias Argentinas 435 (C1405BWE), Buenos Aires, Argentina
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37
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Lim WK, Rösgen J, Englander SW. Urea, but not guanidinium, destabilizes proteins by forming hydrogen bonds to the peptide group. Proc Natl Acad Sci U S A 2009; 106:2595-600. [PMID: 19196963 PMCID: PMC2650309 DOI: 10.1073/pnas.0812588106] [Citation(s) in RCA: 309] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Indexed: 11/18/2022] Open
Abstract
The mechanism by which urea and guanidinium destabilize protein structure is controversial. We tested the possibility that these denaturants form hydrogen bonds with peptide groups by measuring their ability to block acid- and base-catalyzed peptide hydrogen exchange. The peptide hydrogen bonding found appears sufficient to explain the thermodynamic denaturing effect of urea. Results for guanidinium, however, are contrary to the expectation that it might H-bond. Evidently, urea and guanidinium, although structurally similar, denature proteins by different mechanisms.
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Affiliation(s)
- Woon Ki Lim
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104
- Department of Molecular Biology, College of Natural Sciences, Pusan National University, Jangjeon-dong, Keumjeong District, Busan 609-735, South Korea; and
| | - Jörg Rösgen
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555
| | - S. Walter Englander
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104
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38
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SILIGARDI GIULIANO, DRAKE ALEXF, MASCAGNI PAOLO, ROWLANDS DAVIDJ, BROWN FRED, GIBBONS WILLIAMA. A CD strategy for the study of polypeptide folding/unfolding. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1399-3011.1991.tb01535.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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McCarney ER, Kohn JE, Plaxco KW. Is There or Isn't There? The Case for (and Against) Residual Structure in Chemically Denatured Proteins. Crit Rev Biochem Mol Biol 2008; 40:181-9. [PMID: 16126485 DOI: 10.1080/10409230591008143] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
First raised some 60 years ago, the question of whether chemically denatured proteins are fully unfolded has, in recent years, seen significantly renewed interest. This increased attention has been spurred, in large part, by new spectroscopic and computational approaches that suggest even the most highly denatured polypeptides contain significant residual structure. In contrast, the most recent scattering results uphold the long-standing view that chemically denatured proteins adopt random coil configurations. Here we review the evidence both for and against residual structure in chemically denatured proteins, and attempt to reconcile these seemingly contradictory observations.
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Affiliation(s)
- Evan R McCarney
- Department of Chemistry and Biochemistry, University of California, Santa Barbara Santa, Barbara, CA 93106, USA
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40
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Non-random-coil behavior as a consequence of extensive PPII structure in the denatured state. J Mol Biol 2008; 382:203-12. [PMID: 18644382 DOI: 10.1016/j.jmb.2008.07.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 06/21/2008] [Accepted: 07/03/2008] [Indexed: 11/21/2022]
Abstract
Unfolded proteins may contain a native or nonnative residual structure, which has important implications for the thermodynamics and kinetics of folding, as well as for misfolding and aggregation diseases. However, it has been universally accepted that residual structure should not affect the global size scaling of the denatured chain, which obeys the statistics of random coil polymers. Here we use a single-molecule optical technique--fluorescence correlation spectroscopy--to probe the denatured state of a set of repeat proteins containing an increasing number of identical domains, from 2 to 20. The availability of this set allows us to obtain the scaling law for the unfolded state of these proteins, which turns out to be unusually compact, strongly deviating from random coil statistics. The origin of this unexpected behavior is traced to the presence of an extensive nonnative polyproline II helical structure, which we localize to specific segments of the polypeptide chain. We show that the experimentally observed effects of polyproline II on the size scaling of the denatured state can be well-described by simple polymer models. Our findings suggest a hitherto unforeseen potential of nonnative structure to induce significant compaction of denatured proteins, significantly affecting folding pathways and kinetics.
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41
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Footer MJ, Lyo JK, Theriot JA. Close packing of Listeria monocytogenes ActA, a natively unfolded protein, enhances F-actin assembly without dimerization. J Biol Chem 2008; 283:23852-62. [PMID: 18577520 DOI: 10.1074/jbc.m803448200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies of the biochemistry of Listeria monocytogenes virulence protein ActA have typically focused on the behavior of bacteria in complex systems or on the characterization of the protein after expression and purification. Although prior in vivo work has proposed that ActA forms dimers on the surface of L. monocytogenes, dimerization has not been demonstrated in vitro, and little consideration has been given to the surface environment where ActA performs its pivotal role in bacterial actin-based motility. We have synthesized and characterized an ActA dimer and provide evidence that the two ActA molecules do not interact with each other even when tethered together. However, we also demonstrate that artificial dimers provide superior activation of actin nucleation by the Arp2/3 complex compared with monomers and that increased activation of the Arp2/3 complex by dimers may be a general property of Arp2/3 activators. It appears that the close packing ( approximately 19 nm) of ActA molecules on the surface of L. monocytogenes is so dense that the kinetics of actin nucleation mimic that of synthetic ActA dimers. We also present observations indicating that ActA is a natively unfolded protein, largely random coil that is responsible for many of the unique physical properties of ActA including its extended structure, aberrant mobility during SDS-PAGE, and ability to resist irreversible denaturation upon heating.
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Affiliation(s)
- Matthew J Footer
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
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42
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Biophysical characterization of the unstructured cytoplasmic domain of the human neuronal adhesion protein neuroligin 3. Biophys J 2008; 95:1928-44. [PMID: 18456828 DOI: 10.1529/biophysj.107.126995] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cholinesterase-like adhesion molecules (CLAMs) are a family of neuronal cell adhesion molecules with important roles in synaptogenesis, and in maintaining structural and functional integrity of the nervous system. Our earlier study on the cytoplasmic domain of one of these CLAMs, the Drosophila protein, gliotactin, showed that it is intrinsically unstructured in vitro. Bioinformatic analysis suggested that the cytoplasmic domains of other CLAMs are also intrinsically unstructured, even though they bear no sequence homology to each other or to any known protein. In this study, we overexpress and purify the cytoplasmic domain of human neuroligin 3, notwithstanding its high sensitivity to the Escherichia coli endogenous proteases that cause its rapid degradation. Using bioinformatic analysis, sensitivity to proteases, size exclusion chromatography, fluorescence correlation spectroscopy, analytical ultracentrifugation, small angle x-ray scattering, circular dichroism, electron spin resonance, and nuclear magnetic resonance, we show that the cytoplasmic domain of human neuroligin 3 is intrinsically unstructured. However, several of these techniques indicate that it is not fully extended, but becomes significantly more extended under denaturing conditions.
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43
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44
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Pierce V, Kang M, Aburi M, Weerasinghe S, Smith PE. Recent applications of Kirkwood-Buff theory to biological systems. Cell Biochem Biophys 2007; 50:1-22. [PMID: 18043873 PMCID: PMC2566781 DOI: 10.1007/s12013-007-9005-0] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Accepted: 11/02/2007] [Indexed: 12/01/2022]
Abstract
The effect of cosolvents on biomolecular equilibria has traditionally been rationalized using simple binding models. More recently, a renewed interest in the use of Kirkwood-Buff (KB) theory to analyze solution mixtures has provided new information on the effects of osmolytes and denaturants and their interactions with biomolecules. Here we review the status of KB theory as applied to biological systems. In particular, the existing models of denaturation are analyzed in terms of KB theory, and the use of KB theory to interpret computer simulation data for these systems is discussed.
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Affiliation(s)
- Veronica Pierce
- Department of Chemistry, 111 Willard Hall, Kansas State University, Manhattan, KS 66506-3701, USA
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45
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Makowska J, Rodziewicz-Motowidlo S, Baginska K, Makowski M, Vila JA, Liwo A, Chmurzynski L, Scheraga HA. Further evidence for the absence of polyproline II stretch in the XAO peptide. Biophys J 2007; 92:2904-17. [PMID: 17277185 PMCID: PMC1831701 DOI: 10.1529/biophysj.106.097550] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It has been suggested that the alanine-based peptide with sequence Ac-XX-[A](7)-OO-NH(2), termed XAO where X denotes diaminobutyric acid and O denotes ornithine, exists in a predominantly polyproline-helix (P(II)) conformation in aqueous solution. In our recent work, we demonstrated that this "polyproline conformation" should be regarded as a set of local conformational states rather than as the overall conformation of the molecule. In this work, we present further evidence to support this statement. Differential scanning calorimetry measurements showed only a very small peak in the heat capacity of an aqueous solution of XAO at 57 degrees C, whereas the suggested transition to the P(II) structure should occur at approximately 30 degrees C. We also demonstrate that the temperature dependence of the (3)J(HNHalpha) coupling constants of the alanine residues can be explained qualitatively in terms of Boltzmann averaging over all local conformational states; therefore, this temperature dependence proves that a conformational transition does not occur. Canonical MD simulations with the solvent represented by the generalized Born model, and with time-averaged NMR-derived restraints, demonstrate the presence of an ensemble of structures with a substantial amount of local P(II) conformational states but not with an overall P(II) conformation.
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Affiliation(s)
- Joanna Makowska
- Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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46
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Abstract
Recent work on the thermodynamics of protein denatured states is providing insight into the stability of residual structure and the conformational constraints that affect the disordered states of proteins. Current data from native state hydrogen exchange and the pH dependence of protein stability indicate that residual structure can modulate the stability of the denatured state by up to 4 kcal mol(-1). NMR structural data have emphasized the role of hydrophobic clusters in stabilizing denatured state residual structures, however recent results indicate that electrostatic interactions, both favorable and unfavorable, are also important modulators of the stability of the denatured state. Thermodynamics methods that take advantage of histidine-heme ligation chemistry have also been developed to probe the conformational constraints that act on denatured states. These methods have provided insights into the role of excluded volume, chain stiffness, and loop persistence in modulating the conformational preferences of highly disordered proteins. New insights into protein folding and novel methods to manipulate protein stability are emerging from this work.
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Affiliation(s)
- Bruce E Bowler
- Department of Chemistry, University of Montana, Missoula, MT 59812, USA.
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47
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Affiliation(s)
- Zhengshuang Shi
- Department of Chemistry, New York University, 100 Washington Place, New York, New York 10003-5180, USA
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48
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García-Alai MM, Gallo M, Salame M, Wetzler DE, McBride AA, Paci M, Cicero DO, de Prat-Gay G. Molecular basis for phosphorylation-dependent, PEST-mediated protein turnover. Structure 2006; 14:309-19. [PMID: 16472750 DOI: 10.1016/j.str.2005.11.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Revised: 10/26/2005] [Accepted: 11/04/2005] [Indexed: 10/25/2022]
Abstract
Proteasomal-mediated rapid turnover of proteins is often modulated by phosphorylation of PEST sequences. The E2 protein from papillomavirus participates in gene transcription, DNA replication, and episomal genome maintenance. Phosphorylation of a PEST sequence located in a flexible region accelerates its degradation. NMR analysis of a 29 amino acid peptide fragment derived from this region shows pH-dependent polyproline II and alpha helix structures, connected by a turn. Phosphorylation, in particular that at serine 301, disrupts the overall structure, and point mutations have either stabilizing or destabilizing effects. There is an excellent correlation between the thermodynamic stability of different peptides and the half-life of E2 proteins containing the same mutations in vivo. The structure around the PEST region appears to have evolved a marginal stability that is finely tunable by phosphorylation. Thus, conformational stability, rather than recognition of a phosphate modification, modulates the degradation of this PEST sequence by the proteasome machinery.
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49
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Avbelj F, Grdadolnik SG, Grdadolnik J, Baldwin RL. Intrinsic backbone preferences are fully present in blocked amino acids. Proc Natl Acad Sci U S A 2006; 103:1272-7. [PMID: 16423894 PMCID: PMC1360578 DOI: 10.1073/pnas.0510420103] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The preferences of amino acid residues for ,psi backbone angles vary strikingly among the amino acids, as shown by the backbone angle found from the (3)J(H(alpha),H(N)) coupling constant for short peptides in water. New data for the (3)J(H(alpha),H(N)) values of blocked amino acids (dipeptides) are given here. Dipeptides exhibit the full range of coupling constants shown by longer peptides such as GGXGG and dipeptides present the simplest system for analyzing backbone preferences. The dipeptide coupling constants are surprisingly close to values computed from the coil library (conformations of residues not in helices and not in sheets). Published coupling constants for GGXGG peptides agree closely with dipeptide values for all nonpolar residues and for some polar residues but not for X = D, N, T, and Y, which are probably affected by polar side chain-backbone interactions in GGXGG peptides. Thus, intrinsic backbone preferences are already determined at the dipeptide level and remain almost unchanged in GGXGG peptides and are strikingly similar in the coil library of conformations from protein structures. The simplest explanation for the backbone preferences is that backbone conformations are strongly affected by electrostatic dipole-dipole interactions in the peptide backbone and by screening of these interactions with water, which depends on nearby side chains. Strong backbone electrostatic interactions occur in dipeptides. This is shown by calculations both of backbone electrostatic energy for different conformers of the alanine dipeptide in the gas phase and by electrostatic solvation free energies of amino acid dipeptides.
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Affiliation(s)
- Franc Avbelj
- National Institute of Chemistry, Hajdrihova 19, SI 1001 Ljubljana, Slovenia.
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50
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Liu Z, Chen K, Ng A, Shi Z, Woody RW, Kallenbach NR. Solvent Dependence of PII Conformation in Model Alanine Peptides. J Am Chem Soc 2004; 126:15141-50. [PMID: 15548011 DOI: 10.1021/ja047594g] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alanine residues in two model peptides, the pentapeptide AcGGAGGNH(2) and the 11mer AcO(2)A(7)O(2)NH(2), have been reported to have substantial PII conformation in water. The PII structure in both peptides is sensitive to solvent. In the presence of the organic solvent TFE, the conformation of the pentamer changes from PII to internally H-bonded gamma or beta turns, while the chain with seven alanines forms alpha helix. The PII structure in the 11mer is more stable than that in the shorter peptide as the TFE concentration increases. For the pentamer, a comparison of short-chain aliphatic alcohols to water shows that the PII content decreases in the order water > methanol > ethanol > 2-propanol, linearly according to empirical scales of solvent polarity. Thus, depending on the extent of local solvation as folding progresses, the peptide backbone as modeled by alanine oligomers shifts from PII to internally H-bonded (gamma or beta turn) conformations and to alpha helix in longer segments. On the other hand, the PII content of AcO(2)A(7)O(2)NH(2) increases significantly in the presence of guanidine, as does that of oligoproline peptides, while detergent sodium dodecyl sulfate (SDS) favors alpha helix in this peptide. The shorter peptide does not show a parallel increase in PII with guanidine.
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Affiliation(s)
- Zhigang Liu
- Department of Chemistry, New York University, New York, New York 10003, USA
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