1
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Andrews B, Schweitzer-Stenner R, Urbanc B. Intrinsic Conformational Dynamics of Glycine and Alanine in Polarizable Molecular Dynamics Force Fields: Comparison to Spectroscopic Data. J Phys Chem B 2024; 128:6217-6231. [PMID: 38877893 PMCID: PMC11215781 DOI: 10.1021/acs.jpcb.4c02278] [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: 04/09/2024] [Revised: 05/29/2024] [Accepted: 05/30/2024] [Indexed: 06/28/2024]
Abstract
Molecular dynamics (MD) is a great tool for elucidating conformational dynamics of proteins and peptides in water at the atomistic level that often surpasses the level of detail available experimentally. Structure predictions, however, are limited by the accuracy of the underlying MD force field. This limitation is particularly stark in the case of intrinsically disordered peptides and proteins, which are characterized by solvent-accessible and disordered peptide regions and domains. Recent studies show that most additive MD force fields, including CHARMM36m, do not reproduce the intrinsic conformational distributions of guest amino acid residues x in cationic GxG peptides in water in line with experimental data. Positing that a lack of polarizability in additive MD force fields may be the culprit for the reported discrepancies, we here examine the conformational dynamics of guest glycine and alanine residues in cationic GxG peptides in water using two polarizable MD force fields, CHARMM Drude and AMOEBA. Our results indicate that while AMOEBA captures the experimental data better than CHARMM Drude, neither of the two polarizable force fields offers an improvement of the Ramachandran distributions of glycine and alanine residues in cationic GGG and GAG peptides, respectively, over CHARMM36m.
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Affiliation(s)
- Brian Andrews
- Department
of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | | | - Brigita Urbanc
- Department
of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
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2
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Osifová Z, Kalvoda T, Galgonek J, Culka M, Vondrášek J, Bouř P, Bednárová L, Andrushchenko V, Dračínský M, Rulíšek L. What are the minimal folding seeds in proteins? Experimental and theoretical assessment of secondary structure propensities of small peptide fragments. Chem Sci 2024; 15:594-608. [PMID: 38179543 PMCID: PMC10763034 DOI: 10.1039/d3sc04960d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 11/22/2023] [Indexed: 01/06/2024] Open
Abstract
Certain peptide sequences, some of them as short as amino acid triplets, are significantly overpopulated in specific secondary structure motifs in folded protein structures. For example, 74% of the EAM triplet is found in α-helices, and only 3% occurs in the extended parts of proteins (typically β-sheets). In contrast, other triplets (such as VIV and IYI) appear almost exclusively in extended parts (79% and 69%, respectively). In order to determine whether such preferences are structurally encoded in a particular peptide fragment or appear only at the level of a complex protein structure, NMR, VCD, and ECD experiments were carried out on selected tripeptides: EAM (denoted as pro-'α-helical' in proteins), KAM(α), ALA(α), DIC(α), EKF(α), IYI(pro-β-sheet or more generally, pro-extended), and VIV(β), and the reference α-helical CATWEAMEKCK undecapeptide. The experimental data were in very good agreement with extensive quantum mechanical conformational sampling. Altogether, we clearly showed that the pro-helical vs. pro-extended propensities start to emerge already at the level of tripeptides and can be fully developed at longer sequences. We postulate that certain short peptide sequences can be considered minimal "folding seeds". Admittedly, the inherent secondary structure propensity can be overruled by the large intramolecular interaction energies within the folded and compact protein structures. Still, the correlation of experimental and computational data presented herein suggests that the secondary structure propensity should be considered as one of the key factors that may lead to understanding the underlying physico-chemical principles of protein structure and folding from the first principles.
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Affiliation(s)
- Zuzana Osifová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
- Department of Organic Chemistry, Faculty of Science, Charles University Hlavova 2030 Prague 128 00 Czech Republic
| | - Tadeáš Kalvoda
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Jakub Galgonek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Martin Culka
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Jiří Vondrášek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Lucie Bednárová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Valery Andrushchenko
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Martin Dračínský
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
| | - Lubomír Rulíšek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo náměstí 2, 160 00, Praha 6 Czech Republic
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3
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Schweitzer-Stenner R, Kurbaj R, O'Neill N, Andrews B, Shah R, Urbanc B. Conformational Manifold Sampled by Two Short Linear Motif Segments Probed by Circular Dichroism, Vibrational, and Nuclear Magnetic Resonance Spectroscopy. Biochemistry 2023; 62:2571-2586. [PMID: 37595285 DOI: 10.1021/acs.biochem.3c00212] [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: 08/20/2023]
Abstract
Disordered protein segments called short linear motifs (SLiM) serve as recognition sites for a variety of biological processes and act as targeting signals, modification, and ligand binding sites. While SLiMs do not adopt one of the known regular secondary structures, the conformational distribution might still reflect the structural propensities of their amino acid residues and possible interactions between them. In the past, conformational analyses of short peptides provided compelling evidence for the notion that individual residues are less conformationally flexible than locally expected for a random coil. Here, we combined various spectroscopies (NMR, IR, vibrational, and UV circular dichroism) to determine the Ramachandran plots of two SLiM motifs, i.e., GRRDSG and GRRTSG. They are two representatives of RxxS motifs that are capable of being phosphorylated by protein kinase A, an enzyme that plays a fundamental role in a variety of biological processes. Our results reveal that the nearest and non-nearest interactions between residues cause redistributions between polyproline II and β-strand basins while concomitantly stabilizing extended relative to turn-forming and helical structures. They also cause shifts in basin positions. With increasing temperature, β-strand populations become more populated at the expense of polyproline II. While molecular dynamics simulations with Amber ff14SB and CHARMM 36m force fields indicate residue-residue interactions, they do not account for the observed structural changes.
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Affiliation(s)
| | - Raghed Kurbaj
- Department of Chemistry, Drexel University, Philadelphia, PA19104Pennsylvania,United States
| | - Nichole O'Neill
- Department of Chemistry, Drexel University, Philadelphia, PA19104Pennsylvania,United States
| | - Brian Andrews
- Department of Physics, Drexel University, Philadelphia,PA19104Pennsylvania,United States
| | - Riya Shah
- Department of Physics, Drexel University, Philadelphia,PA19104Pennsylvania,United States
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia,PA19104Pennsylvania,United States
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4
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Schweitzer-Stenner R. The relevance of short peptides for an understanding of unfolded and intrinsically disordered proteins. Phys Chem Chem Phys 2023; 25:11908-11933. [PMID: 37096579 DOI: 10.1039/d3cp00483j] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
Abstract
Over the last thirty years the unfolded state of proteins has attracted considerable interest owing to the discovery of intrinsically disordered proteins which perform a plethora of functions despite resembling unfolded proteins to a significant extent. Research on both, unfolded and disordered proteins has revealed that their conformational properties can deviate locally from random coil behavior. In this context results from work on short oligopeptides suggest that individual amino acid residues sample the sterically allowed fraction of the Ramachandran plot to a different extent. Alanine has been found to exhibit a peculiarity in that it has a very high propensity for adopting polyproline II like conformations. This Perspectives article reviews work on short peptides aimed at exploring the Ramachandran distributions of amino acid residues in different contexts with experimental and computational means. Based on the thus provided overview the article discussed to what extent short peptides can serve as tools for exploring unfolded and disordered proteins and as benchmarks for the development of a molecular dynamics force field.
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5
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Yuan Y, Wang F. Dipole Cooperativity and Polarization Frustration Determine the Secondary Structure Distribution of Short Alanine Peptides in Water. J Phys Chem B 2023; 127:3126-3138. [PMID: 36848625 PMCID: PMC10108861 DOI: 10.1021/acs.jpcb.2c07947] [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: 11/11/2022] [Revised: 02/16/2023] [Indexed: 03/01/2023]
Abstract
The physical driving forces for secondary structure preferences of hydrated alanine peptide are investigated with B3LYP-D3(BJ) and the adaptive force matching (AFM) method. The AFM fit to the DFT surface, ALA2022, provides excellent agreement with the nuclear magnetic resonance scalar coupling constants from experiments. In turn, the model is used to gain insight into the physical driving forces behind secondary structure preferences of hydrated peptides. DFT calculations with and without the Conductor-like Screening Model (COSMO) show that the α helix is stabilized by solvent polarization due to dipole cooperativity. The two adjacent amide groups in β strand form a near-planar trapezoid that is not much larger than the size of water molecules. When the finite size of a water molecule is considered, the stabilization from solvent polarization for such a trapezoid is frustrated. Water molecules cannot find orientations to properly stabilize all four polar regions close to each other with such an awkward arrangement. This leads to quite substantial reduction in polarization stabilization. Although the polyproline II (PP-II) conformation is very similar to the β strand, the small twist in the backbone angles allowed much improved polarization stabilization. The improved polarization, when combined with favorable intrapeptide interactions, leads to the PP-II to be lowest in free energy. Other factors, such as the entropic TΔS and the ϕ, ψ coupling terms, are also studied but are found to play only a minor role. The insight shown in this work helps to better understand the structure of globular and intrinsic disordered proteins and facilitate future force field development.
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Affiliation(s)
- Ying Yuan
- Department of Chemistry and
Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Feng Wang
- Department of Chemistry and
Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
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6
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Casier R, Duhamel J. Synergetic Effects of Alanine and Glycine in Blob-Based Methods for Predicting Protein Folding Times. J Phys Chem B 2023; 127:1325-1337. [PMID: 36749707 DOI: 10.1021/acs.jpcb.2c08155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The polypeptide PGlyAlaGlu was prepared with 20 mol % glycine (Gly), 36 mol % d,l-alanine (Ala), and 44 mol % d,l-glutamic acid (Glu) and labeled with the dye 1-pyrenemethylamine to yield a series of Py-PGlyAlaGlu samples. The fluorescence decays of the Py-PGlyAlaGlu samples were analyzed according to the fluorescence blob model (FBM) to obtain the number Nblobexp of amino acids (aa's) encompassed inside the subvolume Vblob of the polypeptide probed by an excited pyrene. An Nblobexp value of 29 (±2) was retrieved for Py-PGlyAlaGlu, which was much larger than for any of the copolypeptide PGlyGlu or PAlaGlu prepared with either Gly and Glu or Ala and Glu, respectively. The continuous increase in Nblobexp with decreasing side chain size (SCS) from 10 aa's for PGlu to 16 aa's for PAlaGlu and 22 aa's for PGlyGlu was used earlier to define the reach of an aa and determine the groups of aa's that could interact with each other along a polypeptide backbone according to their SCS. These groups of aa's, referred to as blobs, led to the implementation of blob-based models (BBM) to predict the folding time τFtheo,BBM of 145 proteins, which was found to match their experimental folding time τFexp with a relatively high 0.71 correlation coefficient. Nevertheless, the much higher Nblobexp value found for Py-PGlyAlaGlu compared to all other pyrene-labeled polypeptides studied to date indicates that the reach of aa's along a polypeptide sequence is affected not only by SCS but also by synergetic effects between different aa's. Following this new insight, a revised BBM was implemented to predict τFtheo,BBM for 195 proteins assuming the existence or absence of synergies to control the interactions between aa's along a polypeptide sequence. Similarly good correlation coefficients of 0.71 and 0.74 were obtained for a direct 1:1 comparison of τFexp and τFtheo,BBM for the 195 proteins without and with synergies, respectively. This result suggests that synergetic effects between different aa's have little effect on τFtheo,BBM predicted from BBM underlying the robustness of this methodology.
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Affiliation(s)
- Remi Casier
- Institute for Polymer Research, Waterloo Institute for Nanotechnology, Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Jean Duhamel
- Institute for Polymer Research, Waterloo Institute for Nanotechnology, Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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7
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O'Neill N, Lima TA, Ferreira FF, Thursch L, Alvarez N, Schweitzer-Stenner R. Forbidden Secondary Structures Found in Gel-Forming Fibrils of Glycylphenylalanylglycine. J Phys Chem B 2022; 126:8080-8093. [PMID: 36194765 DOI: 10.1021/acs.jpcb.2c05010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The zwitterionic l-tripeptide glycylphenylalanylglycine self-assembles into very long crystalline fibrils in an aqueous solution, which causes the formation of an exceptionally strong gel phase (G' ∼ 5 × 106 Pa). The Rietveld refinement analysis of its powder X-ray diffraction (PXRD) pattern reveals a unit cell with four peptides forming a P212121 space group and adopting an inverse polyproline II conformation, that is, a right-handed helical structure that occupies the "forbidden" region of the Ramachandran plot. This unusual structure is stabilized by a plethora of intermolecular interactions facilitated by the large number of different functional groups of the unblocked tripeptide. Comparisons of simulated and experimental Fourier transform infrared and vibrational circular dichroism (VCD) amide I' profiles corroborate the PXRD structure. Our experimental setup reduces the sample to a quasi-two-dimensional network of fibrils. We exploited the influence of this reduced dimensionality on the amide I VCD to identify the main fibril axis. We demonstrate that PXRD, vibrational spectroscopy, and amide I simulations provide a powerful toolset for secondary structure and fibril axis determination.
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Affiliation(s)
- Nichole O'Neill
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States.,Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Thamires A Lima
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Fabio Furlan Ferreira
- Center for Natural and Human Sciences (CCNH), Federal University of ABC (UFABC), Av. Dos Estados, 5001, S622-3, Santo André, São Paulo09210-580, Brazil
| | - Lavenia Thursch
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Nicolas Alvarez
- Department of Chemical Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Reinhard Schweitzer-Stenner
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
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8
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Schweitzer-Stenner R. Exploring Nearest Neighbor Interactions and Their Influence on the Gibbs Energy Landscape of Unfolded Proteins and Peptides. Int J Mol Sci 2022; 23:ijms23105643. [PMID: 35628453 PMCID: PMC9147007 DOI: 10.3390/ijms23105643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/12/2022] [Accepted: 05/13/2022] [Indexed: 11/17/2022] Open
Abstract
The Flory isolated pair hypothesis (IPH) is one of the corner stones of the random coil model, which is generally invoked to describe the conformational dynamics of unfolded and intrinsically disordered proteins (IDPs). It stipulates, that individual residues sample the entire sterically allowed space of the Ramachandran plot without exhibiting any correlations with the conformational dynamics of its neighbors. However, multiple lines of computational, bioinformatic and experimental evidence suggest that nearest neighbors have a significant influence on the conformational sampling of amino acid residues. This implies that the conformational entropy of unfolded polypeptides and proteins is much less than one would expect based on the Ramachandran plots of individual residues. A further implication is that the Gibbs energies of residues in unfolded proteins or polypeptides are not additive. This review provides an overview of what is currently known and what has yet to be explored regarding nearest neighbor interactions in unfolded proteins.
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9
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Milorey B, Schwalbe H, O'Neill N, Schweitzer-Stenner R. Repeating Aspartic Acid Residues Prefer Turn-like Conformations in the Unfolded State: Implications for Early Protein Folding. J Phys Chem B 2021; 125:11392-11407. [PMID: 34619031 DOI: 10.1021/acs.jpcb.1c06472] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein folding can be described as a motion of the polypeptide chain in a potential energy funnel, where the conformational manifold is narrowed as the chain traverses from a completely unfolded state until it reaches the folded (native) state. The initial folding stages set the tone for this process by substantially narrowing the manifold of accessible conformations. In an ideally unfolded state with no long-range stabilizing forces, local conformations (i.e., residual structures) are likely to drive the folding process. While most amino acid residues tend to predominantly adopt extended structures in unfolded proteins and peptides, aspartic acid exhibits a relatively high intrinsic preference for turn-forming conformations. Regions in an unfolded polypeptide or protein that are rich in aspartic acid residues may therefore be crucial sites for protein folding steps. By combining NMR and vibrational spectroscopies, we observed that the conformational sampling of multiple sequentially neighbored aspartic acid residues in the model peptides GDDG and GDDDG even show an on average higher propensity for turn-forming structures than the intrinsic reference system D in GDG, which suggests that nearest neighbor interactions between adjacent aspartic acid residues stabilize local turn-forming structures. In the presence of the unlike neighbor phenylalanine, nearest neighbor interactions are of a totally different nature in that it they decrease the turn-forming propensities and mutually increase the sampling of polyproline II (pPII) conformations. We hypothesize the structural role of aspartic residues in intrinsically disordered proteins in general, and particularly in small linear motifs, that are very much determined by their respective neighbors.
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Affiliation(s)
- Bridget Milorey
- Deparment of Chemistry, Drexel University, Philadelphia, Pennsylvania 19026, United States
| | - Harald Schwalbe
- Institut für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe Universität, Max von Laue Strasse 7, 60438 Frankfurt, Germany
| | - Nichole O'Neill
- Deparment of Chemistry, Drexel University, Philadelphia, Pennsylvania 19026, United States
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10
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Guo M, Rosbottom I, Zhou L, Yong CW, Zhou L, Yin Q, Todorov IT, Errington E, Heng JYY. Triglycine (GGG) Adopts a Polyproline II (pPII) Conformation in Its Hydrated Crystal Form: Revealing the Role of Water in Peptide Crystallization. J Phys Chem Lett 2021; 12:8416-8422. [PMID: 34436909 DOI: 10.1021/acs.jpclett.1c01622] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Polyproline II (pPII) is a left-handed 31-helix conformation, which has been observed to be the most abundant secondary structure in unfolded peptides and proteins compared to α-helix and β-sheet. Although pPII has been reported as the most stable conformation for several unfolded short chain peptides in aqueous solution, it is rarely observed in their solid state. Here, we show for the first time a glycine homopeptide (gly-gly-gly) adopting the pPII conformation in its crystalline dihydrate structure. The single crystal X-ray structure with molecular dynamic simulation suggests that a network of water and the charged carboxylate group is critical in stabilizing the pPII conformation in solid state, offering an insight into the structures of unfolded regions of proteins and the role of water in peptide crystallization.
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Affiliation(s)
| | | | - Lina Zhou
- School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Chin W Yong
- Scientific Computing Department, UKRI Science and Technology Facilities Council, Daresbury Laboratory, Warrington WA4 4AD, U.K
| | - Ling Zhou
- School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Qiuxiang Yin
- School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Ilian T Todorov
- Scientific Computing Department, UKRI Science and Technology Facilities Council, Daresbury Laboratory, Warrington WA4 4AD, U.K
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11
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Schweitzer-Stenner R, Alvarez NJ. Short Peptides as Tunable, Switchable, and Strong Gelators. J Phys Chem B 2021; 125:6760-6775. [PMID: 34133176 DOI: 10.1021/acs.jpcb.1c01447] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This Perspective outlines our current understanding of molecular gels composed of short and ultrashort peptides over the past 20 years. We discuss in detail the state of the art regarding self-assembly mechanisms, structure, thermal stability, and kinetics of fibril and/or network formation. Emphasis is put on the importance of the combined use of spectroscopy and rheology for characterizing and validating self-assembly models. While a range of peptide chemistries are reviewed, we focus our discussion on a unique new class of ultrashort peptide gelators, denoted GxG peptides (x: guest residue), which are capable of forming self-assembled fibril networks. The storage moduli of GxG gels are tunable up to 100 kPa depending on concentration, pH, and/or cosolvent. The sheet structures of the fibrils differ from canonical β-sheets. When appropriate, each section highlights opportunities for additional research and technologies that would further our understanding.
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12
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Rosenberger D, Smith JS, Garcia AE. Modeling of Peptides with Classical and Novel Machine Learning Force Fields: A Comparison. J Phys Chem B 2021; 125:3598-3612. [DOI: 10.1021/acs.jpcb.0c10401] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- David Rosenberger
- Los Alamos National Laboratory, Theoretical Division, Chemistry and Physics of Materials Group, Los Alamos, 87545 New Mexico, United States
- Los Alamos National Laboratory, Theoretical Division, Center for Nonlinear Studies, Los Alamos, 87545 New Mexico, United States
| | - Justin S. Smith
- Los Alamos National Laboratory, Theoretical Division, Chemistry and Physics of Materials Group, Los Alamos, 87545 New Mexico, United States
| | - Angel E. Garcia
- Los Alamos National Laboratory, Theoretical Division, Center for Nonlinear Studies, Los Alamos, 87545 New Mexico, United States
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13
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Yuan Y, Ma Z, Wang F. Development and Validation of a DFT-Based Force Field for a Hydrated Homoalanine Polypeptide. J Phys Chem B 2021; 125:1568-1581. [PMID: 33555880 PMCID: PMC7899179 DOI: 10.1021/acs.jpcb.0c11618] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new force field has been created for simulating hydrated alanine polypeptides using the adaptive force matching (AFM) method. Only density functional theory calculations using the Perdew-Burke-Ernzerhof exchange-correlation functional and the D3 dispersion correction were used to fit the force field. The new force field, AFM2020, predicts NMR scalar coupling constants for hydrated homopolymeric alanine in better agreements with experimental data than several other models including those fitted directly to such data. For Ala7, the new force field shows about 15% helical conformations, 20% conformation in the β basin, and 65% polyproline II. The predicted helical population of short hydrated alanine is higher than previous estimates based on the same experimental data. Gas-phase simulations indicate that the force field developed by AFM solution-phase data is likely to produce a reasonable conformation distribution when hydration water is no longer present, such as the interior of a protein.
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Affiliation(s)
- Ying Yuan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Zhonghua Ma
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Feng Wang
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
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14
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Milorey B, Schweitzer-Stenner R, Andrews B, Schwalbe H, Urbanc B. Short peptides as predictors for the structure of polyarginine sequences in disordered proteins. Biophys J 2021; 120:662-676. [PMID: 33453267 PMCID: PMC7896027 DOI: 10.1016/j.bpj.2020.12.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/08/2020] [Accepted: 12/30/2020] [Indexed: 12/12/2022] Open
Abstract
Intrinsically disordered proteins and intrinsically disordered regions are frequently enriched in charged amino acids. Intrinsically disordered regions are regularly involved in important biological processes in which one or more charged residues is the driving force behind a protein-biomolecule interaction. Several lines of experimental and computational evidence suggest that polypeptides and proteins that carry high net charges have a high preference for extended conformations with average end-to-end distances exceeding expectations for self-avoiding random coils. Here, we show that charged arginine residues even in short glycine-capped model peptides (GRRG and GRRRG) significantly affect the conformational propensities of each other when compared with the intrinsic propensities of a mostly unperturbed arginine in the tripeptide GRG. A conformational analysis based on experimentally determined J-coupling constants from heteronuclear NMR spectroscopy and amide I' band profiles from vibrational spectroscopy reveals that nearest-neighbor interactions stabilize extended β-strand conformations at the expense of polyproline II and turn conformations. The results from molecular dynamics simulations with a CHARMM36m force field and TIP3P water reproduce our results only to a limited extent. The use of the Ramachandran distribution of the central residue of GRRRG in a calculation of end-to-end distances of polyarginines of different length yielded the expected power law behavior. The scaling coefficient of 0.66 suggests that such peptides would be more extended than predicted by a self-avoiding random walk. Our findings thus support in principle theoretical predictions.
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Affiliation(s)
- Bridget Milorey
- Department of Chemistry, Drexel University, Philadelphia, Pennsylvania
| | | | - Brian Andrews
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
| | - Harald Schwalbe
- Institut für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe Universität, Frankfurt, Germany
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania
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15
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Bastida A, Zúñiga J, Requena A, Miguel B, Cerezo J. On the Role of Entropy in the Stabilization of α-Helices. J Chem Inf Model 2020; 60:6523-6531. [PMID: 33280379 DOI: 10.1021/acs.jcim.0c01177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein folding evolves by exploring the conformational space with a subtle balance between enthalpy and entropy changes which eventually leads to a decrease of free energy upon reaching the folded structure. A complete understanding of this process requires, therefore, a deep insight into both contributions to free energy. In this work, we clarify the role of entropy in favoring the stabilization of folded structures in polyalanine peptides with up to 12 residues. We use a novel method referred to as K2V that allows us to obtain the potential-energy landscapes in terms of residue conformations extracted from molecular dynamics simulations at conformational equilibrium and yields folding thermodynamic magnitudes, which are in agreement with the experimental data available. Our results demonstrate that the folded structures of the larger polyalanine chains are stabilized with respect to the folded structures of the shorter chains by both an energetic contribution coming from the formation of the intramolecular hydrogen bonds and an entropic contribution coming from an increase of the entropy of the solvent with approximate weights of 60 and 40%, respectively, thus unveiling a key piece in the puzzle of protein folding. In addition, the ability of the K2V method to provide the enthalpic and entropic contributions for individual residues along the peptide chain makes it clear that the energetic and entropic stabilizations are basically governed by the nearest neighbor residue conformations, with the folding propensity being rationalized in terms of triads of residues.
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Affiliation(s)
- Adolfo Bastida
- Departamento de Química Física, Universidad de Murcia, 30100 Murcia, Spain
| | - José Zúñiga
- Departamento de Química Física, Universidad de Murcia, 30100 Murcia, Spain
| | - Alberto Requena
- Departamento de Química Física, Universidad de Murcia, 30100 Murcia, Spain
| | - Beatriz Miguel
- Departamento de Ingeniería Química y Ambiental, Universidad Politécnica de Cartagena, 30203 Cartagena, Spain
| | - Javier Cerezo
- Departamento de Química, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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16
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Zhang S, Andrews B, Schweitzer-Stenner R, Urbanc B. Intrinsic Conformational Dynamics of Alanine in Water/Ethanol Mixtures: An Experiment-Driven Molecular Dynamics Study. J Phys Chem B 2020; 124:11600-11616. [PMID: 33300341 DOI: 10.1021/acs.jpcb.0c08245] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In vitro, cationic glycylalanylglycine (GAG) forms a hydrogel in binary mixtures of water and ethanol. In water, alanine residue is known for its high polyproline II (pPII) content. Spectroscopic data, including three J-coupling constants and amide I' profiles, indicate that addition of 42% ethanol to water significantly reduces the pPII content of alanine residue in GAG. Here, experiment-based Gaussian Ramachandran distributions of alanine in GAG at different ethanol fractions are examined and three MD force fields are evaluated with respect to their ability to capture these ethanol-induced conformational changes. MD simulations on monomeric GAG in eight different water/ethanol mixtures within Amber ff14SB, OPLS-AA/M, and CHARMM36m reveal that only Amber ff14SB partially captures the ethanol-induced conformational changes of alanine residue in monomeric GAG when 42% ethanol is added to water. MD simulations of 200 mM GAG ensembles in pure water and in the aqueous solution with 42% ethanol showcase the ability of CHARMM36m to capture the effect of ethanol on the average pPII content of alanine in GAG and provide a plausible explanation for this effect, which may stem from an increased propensity of GAG to form oligomers in the presence of ethanol.
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Affiliation(s)
- Shuting Zhang
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Brian Andrews
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | | | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
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17
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Levine MS, Ghosh M, Hesser M, Hennessy N, DiGuiseppi DM, Adler-Abramovich L, Schweitzer-Stenner R. Formation of peptide-based oligomers in dimethylsulfoxide: identifying the precursor of fibril formation. SOFT MATTER 2020; 16:7860-7868. [PMID: 32761042 DOI: 10.1039/d0sm00035c] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The well-studied dipeptide fluorenylmethyloxycarbonyl-di-phenylalanine (FmocFF) forms a rigid hydrogel upon dissolving in dimethylsulfoxide (DMSO) and dilution in H2O. Here, we explored the pre-aggregation of the peptide in pure DMSO by vibrational spectroscopies, X-ray powder diffraction and dynamic light scattering. Our results show an equilibrium between a dominant population of amorphous oligomers (on a length scale of 2 nm) and a small number of protofibrils/fibrils (on a length scale of 30 nm in the centimolar and of 200 nm in the sub-molar region). To probe the mechanism underlying the formation of these protofilaments, we measured the 1H-NMR, IR and visible Raman spectra of DMSO containing different FmocFF concentrations, ranging between 10 and 300 mM. Our data reveal that interpeptide hydrogen bonding leads to the self-assembly of FmocFF in the centimolar region, while π-π stacking between Fmoc-groups is observed above 100 mM. The high 3J(HNHCα) coupling constant of the N-terminal amide proton indicates that the Fmoc end-cap of the peptide locks the N-terminal residue into a conformational ensemble centered at a φ-value of ca. -120°, which corresponds to a parallel β-sheet type conformation. The 3J(HNHCα) coupling constant of the C-terminal residue is indicative of a polyproline II (pPII)/βt mixture. Our results suggest that the gelation of FmocFF caused by the addition of a small amount of water to DMSO mixtures is facilitated by the formation of disordered protofibrils in pure DMSO.
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Affiliation(s)
- Matthew S Levine
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Moumita Ghosh
- Department of Oral Biology, The Goldschleger School of Dental Medicine, Sackler Faculty of Medicine, and The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Morgan Hesser
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Nathan Hennessy
- Department of Chemistry, The University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - David M DiGuiseppi
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA.
| | - Lihi Adler-Abramovich
- Department of Oral Biology, The Goldschleger School of Dental Medicine, Sackler Faculty of Medicine, and The Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv 69978, Israel.
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18
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Glycine in Water Favors the Polyproline II State. Biomolecules 2020; 10:biom10081121. [PMID: 32751224 PMCID: PMC7463814 DOI: 10.3390/biom10081121] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 01/09/2023] Open
Abstract
Conformational preferences of amino acid residues in water are determined by the backbone and side-chain properties. Alanine is known for its high polyproline II (pPII) propensity. The question of relative contributions of the backbone and side chain to the conformational preferences of alanine and other amino acid residues in water is not fully resolved. Because glycine lacks a heavy-atom side chain, glycine-based peptides can be used to examine to which extent the backbone properties affect the conformational space. Here, we use published spectroscopic data for the central glycine residue of cationic triglycine in water to demonstrate that its conformational space is dominated by the pPII state. We assess three commonly used molecular dynamics (MD) force fields with respect to their ability to capture the conformational preferences of the central glycine residue in triglycine. We show that pPII is the mesostate that enables the functional backbone groups of the central residue to form the most hydrogen bonds with water. Our results indicate that the pPII propensity of the central glycine in GGG is comparable to that of alanine in GAG, implying that the water-backbone hydrogen bonding is responsible for the high pPII content of these residues.
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19
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Kumar A, Toal SE, DiGuiseppi D, Schweitzer-Stenner R, Wong BM. Water-Mediated Electronic Structure of Oligopeptides Probed by Their UV Circular Dichroism, Absorption Spectra, and Time-Dependent DFT Calculations. J Phys Chem B 2020; 124:2579-2590. [PMID: 32207305 DOI: 10.1021/acs.jpcb.0c00657] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigate the UV absorption spectra of a series of cationic GxG peptides (where x denotes a guest residue) in aqueous solution and find that only a subset of these spectra show a strong dependence with temperature. To explore whether or not this observation reflects conformational dependencies, we carry out time-dependent density functional calculations for the polyproline II (pPII) and β-strand conformations in implicit and explicit water. We find that the calculated CD spectra for pPII can qualitatively account for the experimental spectra irrespective of the water model. The β-strand UV-CD spectra, however, require the explicit consideration of water. Contrary to conventional wisdom, we find that both the NV1 and NV2 band are the envelopes of contributions from multiple transitions that involve more than just the HOMOs and LUMOs of the peptide groups. A natural transition orbital analysis reveals that some of the transitions have a charge-transfer character. The overall manifold of transitions depends on the peptide's backbone conformation, peptide hydration, and side chain of the guest residue. Our results reveal that peptide groups, side chains, and hydration shells must be considered as an entity for a physically valid characterization of UV absorbance and circular dichroism.
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Affiliation(s)
- Anshuman Kumar
- Department of Chemical & Environmental Engineering, Materials Science & Engineering Program, Department of Chemistry, and Department of Physics & Astronomy, University of California, Riverside, Riverside, California 92521, United States
| | - Siobhan E Toal
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, New Jersey 08028, United States
| | - David DiGuiseppi
- Department of Chemistry, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | | | - Bryan M Wong
- Department of Chemical & Environmental Engineering, Materials Science & Engineering Program, Department of Chemistry, and Department of Physics & Astronomy, University of California, Riverside, Riverside, California 92521, United States
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20
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Keiderling TA. Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques. Chem Rev 2020; 120:3381-3419. [DOI: 10.1021/acs.chemrev.9b00636] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Timothy A. Keiderling
- Department of Chemistry, University of Illinois at Chicago 845 West Taylor Street m/c 111, Chicago, Illinois 60607-7061, United States
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21
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Zhang S, Schweitzer-Stenner R, Urbanc B. Do Molecular Dynamics Force Fields Capture Conformational Dynamics of Alanine in Water? J Chem Theory Comput 2019; 16:510-527. [PMID: 31751129 DOI: 10.1021/acs.jctc.9b00588] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examine the ability of six molecular dynamics (MD) force fields (Amber ff14SB, Amber ff99SBnmr1, Amber ff03ws, OPLS-AA/L, OPLS-AA/M, and CHARMM36) to reproduce conformational ensembles of the central alanine in GAG and AAA in a way that is consistent with five (GAG) or six (AAA) J coupling constants and amide I' profiles. MD-derived Ramachandran plots for all six force fields under study differ from those obtained by the Gaussian fit to experimental data in three major ways: (i) the polyproline II (pPII) basin in the Ramachandran plot is too concentrated, (ii) the antiparallel β (aβ) basin is overpopulated, and (iii) the transitional β (βt) basin is underpopulated. Amber ff14SB outperforms the other five MD force fields and yields the highest pPII populations of the central alanine residue in GAG (55%) and AAA (63%), in good agreement with the predictions of the Gaussian model (59 and 76%). The analysis of the hydration layer around the central alanine residue reveals considerable reorientation of water molecules and reduction in both the average number of water molecules and the average number of water-water hydrogen bonds when glycines (in GAG) are replaced by alanines (in AAA), elucidating water-mediated nearest neighbor effects on alanine's conformational dynamics.
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22
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Feng CJ, Dhayalan B, Tokmakoff A. Refinement of Peptide Conformational Ensembles by 2D IR Spectroscopy: Application to Ala‒Ala‒Ala. Biophys J 2019; 114:2820-2832. [PMID: 29925019 DOI: 10.1016/j.bpj.2018.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 04/27/2018] [Accepted: 05/02/2018] [Indexed: 10/28/2022] Open
Abstract
Characterizing ensembles of intrinsically disordered proteins is experimentally challenging because of the ill-conditioned nature of ensemble determination with limited data and the intrinsic fast dynamics of the conformational ensemble. Amide I two-dimensional infrared (2D IR) spectroscopy has picosecond time resolution to freeze structural ensembles as needed for probing disordered-protein ensembles and conformational dynamics. Also, developments in amide I computational spectroscopy now allow a quantitative and direct prediction of amide I spectra based on conformational distributions drawn from molecular dynamics simulations, providing a route to ensemble refinement against experimental spectra. We performed a Bayesian ensemble refinement method on Ala-Ala-Ala against isotope-edited Fourier-transform infrared spectroscopy and 2D IR spectroscopy and tested potential factors affecting the quality of ensemble refinements. We found that isotope-edited 2D IR spectroscopy provides a stringent constraint on Ala-Ala-Ala conformations and returns consistent conformational ensembles with the dominant ppII conformer across varying prior distributions from many molecular dynamics force fields and water models. The dominant factor influencing ensemble refinements is the systematic frequency uncertainty from spectroscopic maps. However, the uncertainty of conformer populations can be significantly reduced by incorporating 2D IR spectra in addition to traditional Fourier-transform infrared spectra. Bayesian ensemble refinement against isotope-edited 2D IR spectroscopy thus provides a route to probe equilibrium-complex protein ensembles and potentially nonequilibrium conformational dynamics.
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Affiliation(s)
- Chi-Jui Feng
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois
| | - Balamurugan Dhayalan
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois.
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23
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Kumar A, Schweitzer-Stenner R, Wong BM. A new interpretation of the structure and solvent dependence of the far UV circular dichroism spectrum of short oligopeptides. Chem Commun (Camb) 2019; 55:5701-5704. [PMID: 31032831 DOI: 10.1039/c9cc01513b] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
UV circular dichroism (UVCD) spectroscopy is a prominent tool for exploring secondary structures of polypeptides and proteins. In the unfolded state of these biomolecules, most of the individual residues primarily sample a conformation called polyproline II. Its CD spectrum contains a negatively biased positive couplet with a pronounced negative maximum below and a weak positive maximum above 200 nm. It is traditionally rationalized in terms of an excitonic coupling mechanism augmented by polarization effects. In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory's isolated pair hypothesis.
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Affiliation(s)
- Anshuman Kumar
- Department of Chemical & Environmental Engineering, Materials Science & Engineering Program, University of California-Riverside, 900 University Avenue, Riverside, CA 92521, USA.
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24
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Ilawe NV, Schweitzer-Stenner R, DiGuiseppi D, Wong BM. Is a cross-β-sheet structure of low molecular weight peptides necessary for the formation of fibrils and peptide hydrogels? Phys Chem Chem Phys 2019; 20:18158-18168. [PMID: 29696249 DOI: 10.1039/c8cp00691a] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Short peptides have emerged as versatile building blocks for supramolecular structures and hydrogels. In particular, the presence of aromatic amino acid residues and/or aromatic end groups is generally considered to be a prerequisite for initiating aggregation of short peptides into nanotubes or cross β-sheet type fibrils. However, the cationic GAG tripeptide surprisingly violates these rules. Specifically, in water/ethanol mixtures, GAG peptides aggregate into very long crystalline fibrils at temperatures below 35 °C where they eventually form a spanning network structure and, thus, a hydrogel. Two gel phases are formed in this network, and they differ substantially in chirality and thickness of the underlying fibrils, their rheological parameters, and the kinetics of oligomerization, fibrilization, and gel formation. The spectroscopic data strongly suggests that the observed fibrils do not exhibit canonical cross β-sheet structures and are indicative of a yet unknown secondary conformation. To complement our unusual experimental observations in this perspective article, we performed large-scale DFT calculations to probe the geometry and spectroscopic properties of these GAG oligomers. Most importantly, our experimental and computational results yield rather unconventional structures that are not reminiscent of classical cross-β-sheet structures, and we give two extremely likely candidates for oligomer structures that are consistent with experimental amide I' profiles in IR and vibrational circular dichroism (VCD) spectra of the two gel phases.
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Affiliation(s)
- Niranjan V Ilawe
- Department of Chemical & Environmental Engineering, and Materials Science & Engineering Program, University of California-Riverside, Riverside, CA 92521, USA.
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25
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Schweitzer-Stenner R, Toal SE. Anticooperative Nearest-Neighbor Interactions between Residues in Unfolded Peptides and Proteins. Biophys J 2019. [PMID: 29539392 DOI: 10.1016/j.bpj.2018.01.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Growing evidence suggests that the conformational distributions of amino acid residues in unfolded peptides and proteins depend on the nature of the nearest neighbors. To explore whether the underlying interactions would lead to a breakdown of the isolated pair hypothesis of the classical random coil model, we further analyzed the conformational propensities that were recently obtained for the two guest residues (x,y) of GxyG tetrapeptides. We constructed a statistical thermodynamics model that allows for cooperative as well as for anticooperative interactions between adjacent residues adopting either a polyproline II or a β-strand conformation. Our analysis reveals that the nearest-neighbor interactions between most of the central residues in the investigated GxyG peptides are anticooperative. Interaction Gibbs energies are rather large at high temperatures (350 K), at which point many proteins undergo thermal unfolding. At room temperature, these interaction energies are less pronounced. We used the obtained interaction parameter in a Zimm-Bragg/Ising-type approach to calculate the temperature dependence of the ultraviolet circular dichroism (CD) of the MAX3 peptide, which is predominantly built by KV repeats. The agreement between simulation and experimental data was found to be satisfactory. Finally, we analyzed the temperature dependence of the CD and 3J(HNHα) parameters of the amyloid β1-9 fragment. The results of this analysis and a more qualitative consideration of the temperature dependence of denatured proteins probed by CD spectroscopy further corroborate the dominance of anticooperative nearest-neighbor interactions. Generally, our results show that unfolded peptides-and most likely also proteins-exhibit some similarity with antiferromagnetic systems.
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Affiliation(s)
| | - Siobhan E Toal
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania
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26
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Furuta M, Fujisawa T, Urago H, Eguchi T, Shingae T, Takahashi S, Blanch EW, Unno M. Raman optical activity of tetra-alanine in the poly(l-proline) II type peptide conformation. Phys Chem Chem Phys 2018; 19:2078-2086. [PMID: 28045149 DOI: 10.1039/c6cp07828a] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The poly(l-proline) II (PPII) helix is considered to be a major conformation in disordered polypeptides and unfolded proteins in aqueous solution. The PPII conformation can be identified by using Raman optical activity (ROA), which measures the different intensities of right- and left-circularly polarized Raman scattered light from chiral molecules and provides information on stereochemistry associated with vibrational motions. In the present study, we used tetra-alanine (Ala4) as a model system, since its central amide bond adopts the PPII conformation. The predominance of the PPII conformation was supported by 11 ns molecular dynamics (MD) simulations at 300 K. The MD snapshots were used for subsequent quantum mechanical/molecular mechanical (QM/MM) calculations to compute the Raman and ROA spectra. The present MD + QM/MM analysis leads to a good agreement between the observed and simulated spectra, allowing us to assign most of the spectral features including the ROA band near 1320 cm-1, which has been used as a marker for the PPII conformation. This positive ROA band has three components. The lower frequency component near 1310 cm-1 arises from an internal peptide bond, whereas the higher frequency components around 1320-1335 cm-1 appear due to N- and C-terminal peptide groups. The MD + QM/MM calculations also reproduced the electronic circular dichroism spectra of Ala4. The present results provide a satisfactory framework for future investigations of unfolded/disordered proteins as well as peptides in solutions by chiral spectroscopic methods.
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Affiliation(s)
- Masakazu Furuta
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Hiroyasu Urago
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Takahiro Eguchi
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Takahito Shingae
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Satoshi Takahashi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
| | - Ewan W Blanch
- School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan.
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27
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Bag SS, De S. Multipurpose isothiocyanyl alanine/lysine: Use as solvatochromic IR probes and in site specific labeling/ligation of short peptides. Bioorg Med Chem Lett 2018; 28:1404-1409. [PMID: 29555154 DOI: 10.1016/j.bmcl.2018.02.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/27/2018] [Accepted: 02/10/2018] [Indexed: 10/18/2022]
Abstract
The solvatochromic IR responsivity of small side chain -NCS in two unexplored unnatural amino acids, isothiocyanyl alanine (NCSAla = Ita) and lysine (NCSLys = Itl), without perturbing the conformation is demonstrated in two designed short tripeptide (BocAla-NCSAla-Ala-OMe) and hexapeptide (BocLeu-Val-Phe-Phe-NCSLys-Gly-OMe). Demonstration of site specific fluorescent labeling in both the peptides and ligation type reaction in NCSLys indicates the novelty of these two amino acids as alternative to the available canonical amino acids.
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Affiliation(s)
- Subhendu Sekhar Bag
- Bioorganic Chemistry Laboratory, Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
| | - Suranjan De
- Bioorganic Chemistry Laboratory, Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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28
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Lanza G, Chiacchio MA. Quantum Mechanics Study on Hydrophilic and Hydrophobic Interactions in the Trivaline-Water System. J Phys Chem B 2018; 122:4289-4298. [PMID: 29584432 DOI: 10.1021/acs.jpcb.8b00833] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With the aim to elucidate hydrophobic effects in the unfolded state of peptides, DFT-M062X computations on the Val3H+· nH2O ( n up to 22) clusters have been accomplished. As far as the main chain is concerned, four conformers with β-strand and/or polyproline type II conformations, PPII (indicated as β-β, β-PPII, PPII-β, and PPII-PPII), have been found by changing the ϕ and ψ angles. For bare peptide, the side chain (isopropyl) of each residue can independently take on three different orientations with negligible effects on energetics. The great isopropyl spatial separations in β-β and β-PPII conformers allow for the construction of synergic and extensive water-water and water-peptide H-bonding in the minimal hydration Val3H+·22H2O models without significant steric encumbrance. Conversely, due to the proximity of the isopropyl of the central residue with the other two, some restrictions in the water shell construction around the peptide become evident for the PPII-PPII conformer and the number of energetically accessible structures decreases. This is indicative of correlated motion involving isopropyls and backbone mediated by water molecules, the origin of the nearest neighbor effects. Comparing the thermodynamic data of Ala3H+·22H2O and Val3H+·22H2O, what emerges is that both hydration enthalpy and entropy drive the β-strand stability of the latter.
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Affiliation(s)
- Giuseppe Lanza
- Dipartimento di Scienze del Farmaco , Università di Catania , Viale A. Doria 6 , Catania 95125 , Italy
| | - Maria A Chiacchio
- Dipartimento di Scienze del Farmaco , Università di Catania , Viale A. Doria 6 , Catania 95125 , Italy
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29
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Rubio-Martinez J, Tomas MS, Perez JJ. Effect of the solvent on the conformational behavior of the alanine dipeptide deduced from MD simulations. J Mol Graph Model 2017; 78:118-128. [PMID: 29055185 DOI: 10.1016/j.jmgm.2017.10.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 10/07/2017] [Accepted: 10/09/2017] [Indexed: 11/19/2022]
Abstract
In general, peptides do not exhibit a well-defined conformational profile in solution. However, despite the experimental blurred picture associated with their structure, compelling spectroscopic evidence shows that peptides exhibit local order. The conformational profile of a peptide is the result of a balance between intramolecular interactions between different atoms of the molecule and intermolecular interactions between atoms of the molecule and the solvent. Accordingly, the conformational profile of a peptide will change upon the properties of the solvent it is soaked. To get insight into the balance between intra- and intermolecular interactions on the conformational preferences of the peptide backbone we have studied the conformational profile of the alanine dipeptide in diverse solvents using molecular dynamics as sampling technique. Solvents studied include chloroform, methanol, dimethyl sulfoxide, water and N-methylacetamide. Different treatments of the solvent have been studied in the present work including explicit solvent molecules, a generalized Born model and using the bulk dielectric constant of the solvent. The diverse calculations identify four major conformations with different populations in the diverse solvents: the C7eq only sampled in chloroform; the C5 or extended conformation; the polyproline (PII) conformation and the right-handed α-helix conformation (αR). The results of present calculations permit to analyze how the balance between intra- and intermolecular interactions explains the populations of the diverse conformations observed.
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Affiliation(s)
- Jaime Rubio-Martinez
- Dept. of Physical Chemistry, Faculty of Chemistry, Universitat de Barcelona and the Institut de Recerca en Quimica Teorica i Computacional (IQTCUB), Mati i Franques 1-3, 08028 Barcelona, Spain
| | - M Santos Tomas
- Department of Architecture Technology, Universitat Politecnica de Catalunya, Av. Diagonal, 649, E-08028 Barcelona, Spain
| | - Juan J Perez
- Department of Chemical Engineering, Universitat Politecnica de Catalunya- Barcelona Tech, Av. Diagonal, 647, 08028 Barcelona, Spain.
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30
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Schweitzer-Stenner R, Toal SE. Construction and comparison of the statistical coil states of unfolded and intrinsically disordered proteins from nearest-neighbor corrected conformational propensities of short peptides. MOLECULAR BIOSYSTEMS 2017; 12:3294-3306. [PMID: 27545097 DOI: 10.1039/c6mb00489j] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Assessing the influence of nearest neighbors on the conformational ensemble of amino acid residues in unfolded and intrinsically disordered proteins and peptides is pivotal for a thorough understanding of the statistical coil state of unfolded proteins as well as of the energetics of the folding process. Research aimed at exploring nearest neighbor interactions has mostly focused on the analysis of restricted coil libraries that reflect conformational distributions in loops connecting more regular secondary structure segments. Recently, however, Toal et al. reported an experimentally based structural analysis of selected xy-pairs in GxyG tetrapeptides, which revealed quantitative information about conformational changes induced by nearest-neighbor interactions (Eur. J. Chem., 2015, 21, 5173-5192). Here, we perform analyses of Ramachandran plots of xy-pairs in GxyG and in coil libraries (Ting et al., PLOS CompBiol, 2010, 6, e1000763) using Hellinger distances as a quantitative measure of dissimilarities between Ramachandran distributions. Our analysis reveals that nearest-neighbor effects inferred from the above coil library are much less pronounced than corresponding structural changes observed for GxyG peptides. To determine whether nearest-neighbor induced conformational changes observed for GxyG can be utilized for the analysis of unfolded proteins, we analyzed sets of 3J(HHHα) coupling constants of three different unfolded proteins, namely the 130-residue fragment of the Staphylococcus aureus fibronectin-binding protein (FnBPc), denatured hen lysozyme, and the htau40 protein. For the first two proteins we found statistically meaningful correlations between predicted nearest-neighbor induced changes of 3J(HHHα) and experimentally observed deviations from corresponding coupling constants of GxG peptides in water, which we used as reference system with minimal nearest-neighbor interactions. This observation is in line with the NMR based understanding of these proteins being predominantly statistical coils. For htau40, however, which is known to exhibit residual structure and large deviations form statistical coil expectations, these correlations are weak or absent. Our results thus underscore the importance of nearest-neighbor interactions for a complete physical description of an ideal statistical coil state of a protein.
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Affiliation(s)
| | - Siobhan E Toal
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
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31
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Lanza G, Chiacchio MA. Quantum Mechanics Approach to Hydration Energies and Structures of Alanine and Dialanine. Chemphyschem 2017; 18:1586-1596. [PMID: 28371186 DOI: 10.1002/cphc.201700149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Indexed: 11/11/2022]
Abstract
A systematic approach to the phenomena related to hydration of biomolecules is reported at the state of the art of electronic-structure methods. Large-scale CCSD(T), MP4-SDQ, MP2, and DFT(M06-2X) calculations for some hydrated complexes of alanine and dialanine (Ala⋅13 H2 O, Ala2 H+ ⋅18 H2 O, and Ala2 ⋅18 H2 O) are compared with experimental data and other elaborate modeling to assess the reliability of a simple bottom-up approach. The inclusion of a minimal number of water molecules for microhydration of the polar groups together with the polarizable continuum model is sufficient to reproduce the relative bulk thermodynamic functions of the considered biomolecules. These quantities depend on the adopted electronic-structure method, which should be chosen with great care. Nevertheless, the computationally feasible MP2 and M06-2X functionals with the aug-cc-pVTZ basis set satisfactorily reproduce values derived by high-level CCSD(T) and MP4-SDQ methods, and thus they are suitable for future developments of more elaborate and hence more biochemically significant peptides.
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Affiliation(s)
- Giuseppe Lanza
- Dipartimento di Scienze del Farmaco, Università di Catania, Viale A. Doria 6, Catania, 95125, Italy
| | - Maria A Chiacchio
- Dipartimento di Scienze del Farmaco, Università di Catania, Viale A. Doria 6, Catania, 95125, Italy
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32
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Chao WC, Shen JY, Yang CH, Lan YK, Yuan JH, Lin LJ, Yang HC, Lu JF, Wang JS, Wee K, Chen YH, Chou PT. The In Situ Tryptophan Analogue Probes the Conformational Dynamics in Asparaginase Isozymes. Biophys J 2017; 110:1732-1743. [PMID: 27119634 DOI: 10.1016/j.bpj.2016.03.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 03/10/2016] [Accepted: 03/21/2016] [Indexed: 11/19/2022] Open
Abstract
Dynamic water solvation is crucial to protein conformational reorganization and hence to protein structure and functionality. We report here the characterization of water dynamics on the L-asparaginase structural homology isozymes L-asparaginases I (AnsA) and II (AnsB), which are shown via fluorescence spectroscopy and dynamics in combination with molecular dynamics simulation to have distinct catalytic activity. By use of the tryptophan (Trp) analog probe 2,7-diaza-tryptophan ((2,7-aza)Trp), which exhibits unique water-catalyzed proton-transfer properties, AnsA and AnsB are shown to have drastically different local water environments surrounding the single Trp. In AnsA, (2,7-aza)Trp exhibits prominent green N(7)-H emission resulting from water-catalyzed excited-state proton transfer. In stark contrast, the N(7)-H emission is virtually absent in AnsB, which supports a water-accessible and a water-scant environment in the proximity of Trp for AnsA and AnsB, respectively. In addition, careful analysis of the emission spectra and corresponding relaxation dynamics, together with the results of molecular dynamics simulations, led us to propose two structural states associated with the rearrangement of the hydrogen-bond network in the vicinity of Trp for the two Ans. The water molecules revealed in the proximity of the Trp residue have semiquantitative correlation with the observed emission spectral variations of (2,7-aza)Trp between AnsA and AnsB. Titration of aspartate, a competitive inhibitor of Ans, revealed an increase in N(7)-H emission intensity in AnsA but no obvious spectral changes in AnsB. The changes in the emission profiles reflect the modulation of structural states by locally confined environment and trapped-water collective motions.
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Affiliation(s)
- Wei-Chih Chao
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Jiun-Yi Shen
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Cheng-Han Yang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Yi-Kang Lan
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Jui-Hung Yuan
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Li-Ju Lin
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Hsiao-Ching Yang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, Taiwan.
| | - Jyh-Feng Lu
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Jinn-Shyan Wang
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Kevin Wee
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - You-Hua Chen
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan
| | - Pi-Tai Chou
- Department of Chemistry and Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei, Taiwan.
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33
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DiGuiseppi D, Milorey B, Lewis G, Kubatova N, Farrell S, Schwalbe H, Schweitzer-Stenner R. Probing the Conformation-Dependent Preferential Binding of Ethanol to Cationic Glycylalanylglycine in Water/Ethanol by Vibrational and NMR Spectroscopy. J Phys Chem B 2017; 121:5744-5758. [DOI: 10.1021/acs.jpcb.7b02899] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Nina Kubatova
- Institut
für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
| | | | - Harald Schwalbe
- Institut
für Organische Chemie und Chemische Biologie, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
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34
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Lee M, Yoon J, Jang S, Shin S. Conformational sampling of metastable states: Tq-REM as a novel replica exchange method. Phys Chem Chem Phys 2017; 19:5454-5464. [PMID: 28165074 DOI: 10.1039/c6cp05322j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although the replica exchange methods (REMs) were developed as efficient conformational sampling methods for bio-molecular simulations, their application to very large bio-systems is somewhat limited. We propose a new replica exchange scheme (Tq-REM) created by combining the conventional temperature-REM (T-REM) and one of the Hamiltonian-REMs, q-REM, using the effective potential with reduced barriers. In the proposed Tq-REM scheme, high temperature replicas in T-REM are substituted with q-replicas. This combined scheme is expected to exploit advantages of the T-REM and q-REM resulting in improved sampling efficiency while minimizing the drawbacks of both approaches. We investigated the performance of Tq-REM compared with T-REM by performing all-atom MD simulations on Met-enkephalin, (AAQAA)3, and Trpzip2. It was found that convergence of the free energy surfaces was improved by Tq-REM over the conventional T-REM. In particular, the trajectories of Tq-REM were able to sample the relevant conformations for all of the metastable folding intermediates, while some of the local minimum structures are poorly represented by T-REM. The results of the present study suggest that Tq-REM can provide useful tools to investigate systems where metastable states play important roles.
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Affiliation(s)
- MinJun Lee
- Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
| | - Jeseong Yoon
- Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
| | - Soonmin Jang
- Department of Chemistry, Sejong University, Seoul 143-747, Korea
| | - Seokmin Shin
- Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
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35
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Lanza G, Chiacchio MA. Effects of Hydration on the Zwitterion Trialanine Conformation by Electronic Structure Theory. J Phys Chem B 2016; 120:11705-11719. [DOI: 10.1021/acs.jpcb.6b08108] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Giuseppe Lanza
- Dipartimento
di Scienze del
Farmaco, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Maria A. Chiacchio
- Dipartimento
di Scienze del
Farmaco, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
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36
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Margreitter C, Oostenbrink C. Optimization of Protein Backbone Dihedral Angles by Means of Hamiltonian Reweighting. J Chem Inf Model 2016; 56:1823-34. [PMID: 27559757 PMCID: PMC5039763 DOI: 10.1021/acs.jcim.6b00399] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Molecular dynamics
simulations depend critically on the accuracy
of the underlying force fields in properly representing biomolecules.
Hence, it is crucial to validate the force-field parameter sets in
this respect. In the context of the GROMOS force field, this is usually
achieved by comparing simulation data to experimental observables
for small molecules. In this study, we develop new amino acid backbone
dihedral angle potential energy parameters based on the widely used
54A7 parameter set by matching to experimental J values
and secondary structure propensity scales. In order to find the most
appropriate backbone parameters, close to 100 000 different
combinations of parameters have been screened. However, since the
sheer number of combinations considered prohibits actual molecular
dynamics simulations for each of them, we instead predicted the values
for every combination using Hamiltonian reweighting. While the original
54A7 parameter set fails to reproduce the experimental data, we are
able to provide parameters that match significantly better. However,
to ensure applicability in the context of larger peptides and full
proteins, further studies have to be undertaken.
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Affiliation(s)
- Christian Margreitter
- Institute for Molecular Modeling and Simulation, University of Natural Resources and Life Sciences , Muthgasse 18, 1190 Vienna, Austria
| | - Chris Oostenbrink
- Institute for Molecular Modeling and Simulation, University of Natural Resources and Life Sciences , Muthgasse 18, 1190 Vienna, Austria
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37
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Farrell S, DiGuiseppi D, Alvarez N, Schweitzer-Stenner R. The interplay of aggregation, fibrillization and gelation of an unexpected low molecular weight gelator: glycylalanylglycine in ethanol/water. SOFT MATTER 2016; 12:6096-6110. [PMID: 27363780 DOI: 10.1039/c6sm00879h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Hydrogels formed by polypeptides could be much-favored tools for drug delivery because their main ingredients are generally biodegradable. However, the gelation of peptides in aqueous solution generally requires a minimal length of the peptide as well as distinct sequences of hydrophilic and hydrophobic residues. The aggregation of short peptides like tripeptides, which are relatively cheap and offer a high degree of biodegradability, are generally thought to require a high hydrophobicity of their residues. We found that contrary to this expectation cationic glycylalanylglycine in 55 mol% ethanol/45 mol% water forms a gel below a melting temperature of ca. 36 °C. A pure hydrogel state can be obtained after allowing the ethanol component to evaporate. The gel phase consists of crystalline fibrils of several 100 μm, which form a sample-spanning network. Rheological data reveal a soft elastic solid gel. We investigated the kinetics of the various processes that lead to the final gel state of the ternary mixture by a unique combination of UV circular dichroism, infrared, vibrational circular dichroism (VCD) and rheological measurements. A mathematical analysis of our data show that gelation is preceded by the formation of peptide β-sheet like tapes or ribbons, which give rise to a significant enhancement of the amide I' VCD signal, and the subsequent formation of rather thick and long fibrils. The VCD signals indicate that the tapes exhibit a right-handed helicity at temperatures above 16 °C and a left-handed helicity below. The tapes'/ribbons' helicity change occurs at a temperature where the UVCD data reflect a relatively long nucleation process. The kinetics of gel formation probed by the storage and loss moduli are composed of a fast process that follows tape/ribbon/fibril formation and is clearly identifiable in a movie that shows the gelation process and a slow process that causes an additional gel stabilization. The rheological data indicate that left-handed fibrils observed at low temperatures form a more solid-like structure than their right-handed counterparts formed at higher temperatures. Taken together our data reveal GAG as an unexpected gelator, the formation of which is underlied by a set of distinguishable kinetic processes.
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Affiliation(s)
- Stefanie Farrell
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
| | - David DiGuiseppi
- Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA.
| | - Nicolas Alvarez
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
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38
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Milorey B, Farrell S, Toal SE, Schweitzer-Stenner R. Demixing of water and ethanol causes conformational redistribution and gelation of the cationic GAG tripeptide. Chem Commun (Camb) 2016; 51:16498-501. [PMID: 26414527 DOI: 10.1039/c5cc06097d] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The cationic tripeptide GAG undergoes three conformational changes in binary mixtures of water and ethanol. At 17 mol% of ethanol conformational sampling is shifted from pPII towards β-strands. A more pronounced shift in the same direction occurs at 40 mol%. At ca. 55 mol% of ethanol and above a peptide concentration of ca. 0.2 M the ternary peptide-water-ethanol mixture forms a hydrogel which is comprised of unusually large crystalline like non-β sheet fibrils forming a sample spanning matrix.
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Affiliation(s)
- Bridget Milorey
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA, USA.
| | - Stefanie Farrell
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA, USA.
| | - Siobhan E Toal
- Department of Chemistry, University of Pennsylvania, 231, South 34th-Street, Philadelphia, PA 19104, USA
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39
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Ilawe NV, Raeber AE, Schweitzer-Stenner R, Toal SE, Wong BM. Assessing backbone solvation effects in the conformational propensities of amino acid residues in unfolded peptides. Phys Chem Chem Phys 2016; 17:24917-24. [PMID: 26343224 DOI: 10.1039/c5cp03646a] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Conformational ensembles of individual amino acid residues within model GxG peptides (x representing different amino acid residues) are dominated by a mixture of polyproline II (pPII) and β-strand like conformations. We recently discovered rather substantial differences between the enthalpic and entropic contributions to this equilibrium for different amino acid residues. Isoleucine and valine exceed all other amino acid residues in terms of their rather large enthalpic stabilization and entropic destabilization of polyproline II. In order to shed light on these underlying physical mechanisms, we performed high-level DFT calculations to explore the energetics of four representative GxG peptides where x = alanine (A), leucine (L), valine (V), and isoleucine (I) in explicit water (10 H2O molecules with a polarizable continuum water model) and in vacuo. We found that the large energetic contributions to the stabilization of pPII result, to a major extent, from peptide-water, water-water interactions, and changes of the solvent self-energy. Differences between the peptide-solvent interaction energies of hydration in pPII and β-strand peptides are particularly important for the pPII ⇌ β equilibria of the more aliphatic peptides GIG and GLG. Furthermore, we performed a vibrational analysis of the four peptides in both conformations and discovered a rather substantial mixing between water motions and peptide vibrations below 700 cm(-1). We found that the respective vibrational entropies are substantially different for the considered conformations, and their contributions to the Gibbs/Helmholtz energy stabilize β-strand conformations. Taken together, our results underscore the notion of the solvent being the predominant determinant of peptide (and protein) conformations in the unfolded state.
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Affiliation(s)
- Niranjan V Ilawe
- Department of Chemical & Environmental Engineering, and Materials Science & Engineering Program, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
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40
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Li S, Andrews CT, Frembgen-Kesner T, Miller MS, Siemonsma SL, Collingsworth TD, Rockafellow IT, Ngo NA, Campbell BA, Brown RF, Guo C, Schrodt M, Liu YT, Elcock AH. Molecular Dynamics Simulations of 441 Two-Residue Peptides in Aqueous Solution: Conformational Preferences and Neighboring Residue Effects with the Amber ff99SB-ildn-NMR Force Field. J Chem Theory Comput 2016; 11:1315-29. [PMID: 26579777 DOI: 10.1021/ct5010966] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the intrinsic conformational preferences of amino acids and the extent to which they are modulated by neighboring residues is a key issue for developing predictive models of protein folding and stability. Here we present the results of 441 independent explicit-solvent MD simulations of all possible two-residue peptides that contain the 20 standard amino acids with histidine modeled in both its neutral and protonated states. (3)J(HNHα) coupling constants and δ(Hα) chemical shifts calculated from the MD simulations correlate quite well with recently published experimental measurements for a corresponding set of two-residue peptides. Neighboring residue effects (NREs) on the average (3)J(HNHα) and δ(Hα) values of adjacent residues are also reasonably well reproduced, with the large NREs exerted experimentally by aromatic residues, in particular, being accurately captured. NREs on the secondary structure preferences of adjacent amino acids have been computed and compared with corresponding effects observed in a coil library and the average β-turn preferences of all amino acid types have been determined. Finally, the intrinsic conformational preferences of histidine, and its NREs on the conformational preferences of adjacent residues, are both shown to be strongly affected by the protonation state of the imidazole ring.
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Affiliation(s)
- Shuxiang Li
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Casey T Andrews
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | | | - Mark S Miller
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Stephen L Siemonsma
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | | | - Isaac T Rockafellow
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Nguyet Anh Ngo
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Brady A Campbell
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Reid F Brown
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Chengxuan Guo
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Michael Schrodt
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Yu-Tsan Liu
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
| | - Adrian H Elcock
- Department of Biochemistry, University of Iowa , Iowa City, Iowa 52242, United States
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41
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Almeida GG, Cordeiro JMM, Martín ME, Aguilar MA. Conformational Changes of the Alanine Dipeptide in Water–Ethanol Binary Mixtures. J Chem Theory Comput 2016; 12:1514-24. [DOI: 10.1021/acs.jctc.5b00952] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Glauco G. Almeida
- Faculdade de Engenharia,
Universidade Estadual Paulista “Julio de Mesquita Filho″, Ilha Solteira 15385-000, Brasil
| | - João M. M. Cordeiro
- Faculdade de Engenharia,
Universidade Estadual Paulista “Julio de Mesquita Filho″, Ilha Solteira 15385-000, Brasil
| | - M. Elena Martín
- Área
de Química Física, University of Extremadura, Avda.
Elvas s/n, Edif. José Ma Viguera
Lobo, 3a planta, Badajoz 06006, Spain
| | - Manuel A. Aguilar
- Área
de Química Física, University of Extremadura, Avda.
Elvas s/n, Edif. José Ma Viguera
Lobo, 3a planta, Badajoz 06006, Spain
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42
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Bastida A, Zúñiga J, Requena A, Miguel B, Candela ME, Soler MA. Conformational Changes of Trialanine in Water Induced by Vibrational Relaxation of the Amide I Mode. J Phys Chem B 2016; 120:348-57. [PMID: 26690744 DOI: 10.1021/acs.jpcb.5b09753] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Most of the protein-based diseases are caused by anomalies in the functionality and stability of these molecules. Experimental and theoretical studies of the conformational dynamics of proteins are becoming in this respect essential to understand the origin of these anomalies. However, a description of the conformational dynamics of proteins based on mechano-energetic principles still remains elusive because of the intrinsic high flexibility of the peptide chains, the participation of weak noncovalent interactions, and the role of the ubiquitous water solvent. In this work, the conformational dynamics of trialanine dissolved in water (D2O) is investigated through Molecular Dynamics (MD) simulations combined with instantaneous normal modes (INMs) analysis both at equilibrium and after the vibrational excitation of the C-terminal amide I mode. The conformational equilibrium between α and pPII conformers is found to be altered by the intramolecular relaxation of the amide I mode as a consequence of the different relaxation pathways of each conformer which modify the amount of vibrational energy stored in the torsional motions of the tripeptide, so the α → pPII and pPII → α conversion rates are increased differently. The selectivity of the process comes from the shifts of the vibrational frequencies with the conformational changes that modify the resonance conditions driving the intramolecular energy flows.
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Affiliation(s)
- Adolfo Bastida
- Departamento de Química Física, Universidad de Murcia , 30100 Murcia, Spain
| | - José Zúñiga
- Departamento de Química Física, Universidad de Murcia , 30100 Murcia, Spain
| | - Alberto Requena
- Departamento de Química Física, Universidad de Murcia , 30100 Murcia, Spain
| | - Beatriz Miguel
- Departamento de Ingeniería Química y Ambiental, Universidad Politécnica de Cartagena , 30203 Cartagena, Spain
| | | | - Miguel Angel Soler
- Department of Medical and Biological Sciences, University of Udine , 33100 Udine, Italy
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43
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He E, Yan G, Zhang J, Wang J, Li W. Effects of phosphorylation on the intrinsic propensity of backbone conformations of serine/threonine. J Biol Phys 2016; 42:247-58. [PMID: 26759163 DOI: 10.1007/s10867-015-9405-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 11/18/2015] [Indexed: 11/28/2022] Open
Abstract
Each amino acid has its intrinsic propensity for certain local backbone conformations, which can be further modulated by the physicochemical environment and post-translational modifications. In this work, we study the effects of phosphorylation on the intrinsic propensity for different local backbone conformations of serine/threonine by molecular dynamics simulations. We showed that phosphorylation has very different effects on the intrinsic propensity for certain local backbone conformations for the serine and threonine. The phosphorylation of serine increases the propensity of forming polyproline II, whereas that of threonine has the opposite effect. Detailed analysis showed that such different responses to phosphorylation mainly arise from their different perturbations to the backbone hydration and the geometrical constraints by forming side-chain-backbone hydrogen bonds due to phosphorylation. Such an effect of phosphorylation on backbone conformations can be crucial for understanding the molecular mechanism of phosphorylation-regulated protein structures/dynamics and functions.
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Affiliation(s)
- Erbin He
- National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, 210093, People's Republic of China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Guanghui Yan
- Department of Mathematics and Physics, Nanjing Institute of Technology, Nanjing, 211167, People's Republic of China
| | - Jian Zhang
- National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, 210093, People's Republic of China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Jun Wang
- National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, 210093, People's Republic of China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China.
| | - Wenfei Li
- National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing, 210093, People's Republic of China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China.
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44
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Kaminský J, Jensen F. Conformational Interconversions of Amino Acid Derivatives. J Chem Theory Comput 2016; 12:694-705. [PMID: 26691979 DOI: 10.1021/acs.jctc.5b00911] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Exhaustive conformational interconversions including transition structure analyses of N-acetyl-l-glycine-N-methylamide as well as its alanine, serine, and cysteine analogues have been investigated at the MP2/6-31G** level, yielding a total of 142 transition states. Improved estimates of relative energies were obtained by separately extrapolating the Hartree-Fock and MP2 energies to the basis set limit and adding the difference between CCSD(T) and MP2 results with the cc-pVDZ basis set to the extrapolated MP2 results. The performance of eight empirical force fields (AMBER94, AMBER14SB, MM2, MM3, MMFFs, CHARMM22_CMAP, OPLS_2005, and AMOEBAPRO13) in reproducing ab initio energies of transition states was tested. Our results indicate that commonly used class I force fields employing a fixed partial charge model for the electrostatic interaction provide mean errors in the ∼10 kJ/mol range for energies of conformational transition states for amino acid conformers. Modern reparametrized versions, such as CHARMM22_CMAP, and polarizable force fields, such as AMOEBAPRO13, have slightly lower mean errors, but maximal errors are still in the 35 kJ/mol range. There are differences between the force fields in their ability for reproducing conformational transitions classified according to backbone/side-chain or regions in the Ramachandran angles, but the data set is likely too small to draw any general conclusions. Errors in conformational interconversion barriers by ∼10 kJ/mol suggest that the commonly used force field may bias certain types of transitions by several orders of magnitude in rate and thus lead to incorrect dynamics in simulations. It is therefore suggested that information for conformational transition states should be included in parametrizations of new force fields.
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Affiliation(s)
- Jakub Kaminský
- Institute of Organic Chemistry and Biochemistry, Flemingovo nám. 2, 166 10 Prague, Czech Republic
| | - Frank Jensen
- Department of Chemistry, Aarhus University , Langelandsgade 140, DK-8000 Aarhus C, Denmark
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Meral D, Toal S, Schweitzer-Stenner R, Urbanc B. Water-Centered Interpretation of Intrinsic pPII Propensities of Amino Acid Residues: In Vitro-Driven Molecular Dynamics Study. J Phys Chem B 2015; 119:13237-51. [PMID: 26418575 DOI: 10.1021/acs.jpcb.5b06281] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amino acid residues of unfolded peptides in water sample only a few basins in the Ramachandran plot, including prominent polyproline II-like (pPII) conformations. Dynamics of guest residues, X, in GXG peptides in water were recently reported to be dominated by pPII and β-strand-like (β) conformations, resulting in an enthalpy-entropy compensation at ∼300 K. Using molecular dynamics (MD) in explicit solvent, we here examine pPII and β conformational ensembles of 15 guest residues in GXG peptides, quantify local orientation of water around their side chains through novel water orientation plots, and study their hydration and hydrogen bonding properties. We show that pPII and β ensembles are characterized by distinct water orientations: pPII ensembles are associated with an increased population of water oriented in parallel to the side chain surface whereas β ensembles exhibit more heterogeneous water orientations. The backbone hydration is significantly higher in pPII than in β ensembles. Importantly, pPII to β hydration differences and the solvent accessible surface area of Cβ hydrogens both correlate with experimental pPII propensities. We propose that pPII conformations are stabilized by a local, hydrogen-bonded clathrate-like water structure and that residue-specific intrinsic pPII propensities reflect distinct abilities of side chains to template this water structure.
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Affiliation(s)
- Derya Meral
- Department of Physics, Drexel University , Philadelphia, Pennsylvania 19104, United States
| | - Siobhan Toal
- Department of Chemistry, Drexel University , Philadelphia, Pennsylvania 19104, United States
| | | | - Brigita Urbanc
- Department of Physics, Drexel University , Philadelphia, Pennsylvania 19104, United States.,Faculty of Mathematics and Physics, University of Ljubljana , 1000 Ljubljana, Slovenia
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Schweitzer-Stenner R, Toal SE. Entropy reduction in unfolded peptides (and proteins) due to conformational preferences of amino acid residues. Phys Chem Chem Phys 2015; 16:22527-36. [PMID: 25227444 DOI: 10.1039/c4cp02108h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
As established by several groups over the last 20 years, amino acid residues in unfolded peptides and proteins do not exhibit the unspecific random distribution as assumed by the classical random coil model. Individual amino acid residues in small peptides were found to exhibit different conformational preferences. Here, we utilize recently obtained conformational distributions of guest amino acid residues in GxG peptides to estimate their conformational entropy, which we find to be significantly lower than the entropy of an assumed random coil like distribution. Only at high temperature do backbone entropies approach random coil like values. We utilized the obtained backbone entropies of the investigated amino acid residues to estimate the loss of conformational entropy caused by a coil → helix transition and identified two subsets of amino acid residues for which the thus calculated entropy losses correlate well with the respective Gibbs energy of helix formation obtained for alanine based host-guest systems. Calculated and experimentally derived entropic losses were found to be in good agreement. For most of the amino acid residues investigated entropic losses derived from our GxG distributions correlate very well with corresponding values recently obtained from MD simulations biased by conformational propensities derived from truncated coil libraries. Both, conformational entropy and the entropy of solvation exhibit a strong, residue specific temperature dependence, which can be expected to substantially affect the stability of unfolded states. Altogether, our results provide strong evidence for the notion that conformational preferences of amino acid residues matter with regard to the thermodynamics of peptide and protein folding.
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Gao Y, Li Y, Mou L, Hu W, Zheng J, Zhang JZH, Mei Y. Coupled Two-Dimensional Main-Chain Torsional Potential for Protein Dynamics II: Performance and Validation. J Phys Chem B 2015; 119:4188-93. [DOI: 10.1021/jp510215c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Ya Gao
- College
of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620, China
| | - Yongxiu Li
- College
of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620, China
- Key
Laboratory of Catalysis and Materials Science of the State Ethnic
Affairs Commission and Ministry of Education, Hubei Province, South-Central University for Nationalities, Wuhan 430074, China
| | - Lirong Mou
- Institutes
for Advanced Interdisciplinary Research, East China Normal University, Shanghai 200062, China
| | - Wenxin Hu
- Computing Center, School of Information Science & Technology, East China Normal University, Shanghai 200062, China
| | - Jun Zheng
- Computing Center, School of Information Science & Technology, East China Normal University, Shanghai 200062, China
| | - John Z. H. Zhang
- College
of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620, China
- NYU-ECNU Center
for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
| | - Ye Mei
- Center
for Laser and Computational Biophysics, State Key Laboratory of Precision
Spectroscopy, Department of Physics and Institute of Theoretical and
Computational Science, East China Normal University, Shanghai 200062, China
- NYU-ECNU Center
for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
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Toal SE, Kubatova N, Richter C, Linhard V, Schwalbe H, Schweitzer-Stenner R. Randomizing the unfolded state of peptides (and proteins) by nearest neighbor interactions between unlike residues. Chemistry 2015; 21:5173-92. [PMID: 25728043 DOI: 10.1002/chem.201406539] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Indexed: 12/29/2022]
Abstract
To explore the influence of nearest neighbors on conformational biases in unfolded peptides, we combined vibrational and 2D NMR spectroscopy to obtain the conformational distributions of selected "GxyG" host-guest peptides in aqueous solution: GDyG, GSyG, GxLG, GxVG, where x/y=A, K, L, V. Large changes of conformational propensities were observed due to nearest-neighbor interactions, at variance with the isolated pair hypothesis. We found that protonated aspartic acid and serine lose their above-the-average preference for turn-like structures in favor of polyproline II (pPII) populations in the presence of neighbors with bulky side chains. Such residues also decrease the above-the-average pPII preference of alanine. These observations suggest that the underlying mechanism involves a disruption of the hydration shell. Thermodynamic analysis of (3) J(H(N) ,H(α) ) (T) data for each x,y residue reveals that modest changes in the conformational ensemble masks larger changes of enthalpy and entropy governing the pPII↔β equilibrium indicating a significant residue dependent temperature dependence of the peptides' conformational ensembles. These results suggest that nearest-neighbor interactions between unlike residues act as conformational randomizers close to the enthalpy-entropy compensation temperature, eliminating intrinsic biases in favor of largely balanced pPII/β dominated ensembles at physiological temperatures.
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Affiliation(s)
- Siobhan E Toal
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 10104 (USA); Present address: Department of Biophysics and Biochemistry, Yale University, New Haven, CT 06250 (USA)
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Lanza G, Chiacchio MA. Interfacial water at the trialanine hydrophilic surface: a DFT electronic structure and bottom-up investigation. Phys Chem Chem Phys 2015; 17:17101-11. [DOI: 10.1039/c5cp00270b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A model describing a network of hydrogen bonded water-trialanine has been developed to estimate hydration effects on various conformers of the peptide.
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Affiliation(s)
- Giuseppe Lanza
- Dipartimento di Scienze del Farmaco
- Università di Catania
- 95125 Catania
- Italy
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50
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Xiao X, Kallenbach N, Zhang Y. Peptide Conformation Analysis Using an Integrated Bayesian Approach. J Chem Theory Comput 2014; 10:4152-4159. [PMID: 25221447 PMCID: PMC4159213 DOI: 10.1021/ct500433d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Indexed: 01/22/2023]
Abstract
Unlike native proteins that are amenable to structural analysis at atomic resolution, unfolded proteins occupy a manifold of dynamically interconverting structures. Defining the conformations of unfolded proteins is of significant interest and importance, for folding studies and for understanding the properties of intrinsically disordered proteins. Short chain protein fragments, i.e., oligopeptides, provide an excellent test-bed in efforts to define the conformational ensemble of unfolded chains. Oligomers of alanine in particular have been extensively studied as minimalist models of the intrinsic conformational preferences of the peptide backbone. Even short alanine peptides occupy an ensemble of substates that are distinguished by small free energy differences, so that the problem of quantifying the conformational preferences of the backbone remains a fundamental challenge in protein biophysics. Here, we demonstrate an integrated computational-experimental-Bayesian approach to quantify the conformational ensembles of the model trialanine peptide in water. In this approach, peptide conformational substates are first determined objectively by clustering molecular dynamics snapshots based on both structural and dynamic information. Next, a set of spectroscopic data for each conformational substate is computed. Finally, a Bayesian statistical analysis of both experimentally measured spectroscopic data and computational results is carried out to provide a current best estimate of the substate population ensemble together with corresponding confidence intervals. This distribution of substates can be further systematically refined with additional high-quality experimental data and more accurate computational modeling. Using an experimental data set of NMR coupling constants, we have also applied this approach to characterize the conformation ensemble of trivaline in water.
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Affiliation(s)
- Xia Xiao
- Department of Chemistry, New York University , New York, New York 10003, United States
| | - Neville Kallenbach
- Department of Chemistry, New York University , New York, New York 10003, United States
| | - Yingkai Zhang
- Department of Chemistry, New York University , New York, New York 10003, United States ; NYU-ECNU Center for Computational Chemistry at NYU Shanghai , Shanghai 200062, China
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