1
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Ille AM, Markosian C, Burley SK, Mathews MB, Pasqualini R, Arap W. Generative artificial intelligence performs rudimentary structural biology modeling. Sci Rep 2024; 14:19372. [PMID: 39169047 PMCID: PMC11339285 DOI: 10.1038/s41598-024-69021-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 07/30/2024] [Indexed: 08/23/2024] Open
Abstract
Natural language-based generative artificial intelligence (AI) has become increasingly prevalent in scientific research. Intriguingly, capabilities of generative pre-trained transformer (GPT) language models beyond the scope of natural language tasks have recently been identified. Here we explored how GPT-4 might be able to perform rudimentary structural biology modeling. We prompted GPT-4 to model 3D structures for the 20 standard amino acids and an α-helical polypeptide chain, with the latter incorporating Wolfram mathematical computation. We also used GPT-4 to perform structural interaction analysis between the anti-viral nirmatrelvir and its target, the SARS-CoV-2 main protease. Geometric parameters of the generated structures typically approximated close to experimental references. However, modeling was sporadically error-prone and molecular complexity was not well tolerated. Interaction analysis further revealed the ability of GPT-4 to identify specific amino acid residues involved in ligand binding along with corresponding bond distances. Despite current limitations, we show the current capacity of natural language generative AI to perform basic structural biology modeling and interaction analysis with atomic-scale accuracy.
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Affiliation(s)
- Alexander M Ille
- School of Graduate Studies, Rutgers, The State University of New Jersey, Newark, NJ, USA
- Rutgers Cancer Institute, Newark, NJ, USA
- Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Christopher Markosian
- School of Graduate Studies, Rutgers, The State University of New Jersey, Newark, NJ, USA
- Rutgers Cancer Institute, Newark, NJ, USA
- Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Stephen K Burley
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
- Rutgers Cancer Institute, New Brunswick, NJ, USA
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer Center, University of California-San Diego, La Jolla, San Diego, CA, USA
| | - Michael B Mathews
- School of Graduate Studies, Rutgers, The State University of New Jersey, Newark, NJ, USA
- Division of Infectious Disease, Department of Medicine, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Renata Pasqualini
- Rutgers Cancer Institute, Newark, NJ, USA.
- Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, NJ, USA.
| | - Wadih Arap
- Rutgers Cancer Institute, Newark, NJ, USA.
- Division of Hematology/Oncology, Department of Medicine, Rutgers New Jersey Medical School, Newark, NJ, USA.
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2
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Myšková A, Sýkora D, Kuneš J, Maletínská L. Lipidization as a tool toward peptide therapeutics. Drug Deliv 2023; 30:2284685. [PMID: 38010881 PMCID: PMC10987053 DOI: 10.1080/10717544.2023.2284685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Accepted: 11/12/2023] [Indexed: 11/29/2023] Open
Abstract
Peptides, as potential therapeutics continue to gain importance in the search for active substances for the treatment of numerous human diseases, some of which are, to this day, incurable. As potential therapeutic drugs, peptides have many favorable chemical and pharmacological properties, starting with their great diversity, through their high affinity for binding to all sort of natural receptors, and ending with the various pathways of their breakdown, which produces nothing but amino acids that are nontoxic to the body. Despite these and other advantages, however, they also have their pitfalls. One of these disadvantages is the very low stability of natural peptides. They have a short half-life and tend to be cleared from the organism very quickly. Their instability in the gastrointestinal tract, makes it impossible to administer peptidic drugs orally. To achieve the best pharmacologic effect, it is desirable to look for ways of modifying peptides that enable the use of these substances as pharmaceuticals. There are many ways to modify peptides. Herein we summarize the approaches that are currently in use, including lipidization, PEGylation, glycosylation and others, focusing on lipidization. We describe how individual types of lipidization are achieved and describe their advantages and drawbacks. Peptide modifications are performed with the goal of reaching a longer half-life, reducing immunogenicity and improving bioavailability. In the case of neuropeptides, lipidization aids their activity in the central nervous system after the peripheral administration. At the end of our review, we summarize all lipidized peptide-based drugs that are currently on the market.
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Affiliation(s)
- Aneta Myšková
- Department of Analytical Chemistry, University of Chemistry and Technology Prague, Prague, Czech Republic
- Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
| | - David Sýkora
- Department of Analytical Chemistry, University of Chemistry and Technology Prague, Prague, Czech Republic
| | - Jaroslav Kuneš
- Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Lenka Maletínská
- Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
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3
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Spiliopoulou M, Karavassili F, Triandafillidis DP, Valmas A, Fili S, Kosinas C, Barlos K, Barlos KK, Morin M, Reinle-Schmitt ML, Gozzo F, Margiolaki I. New perspectives in macromolecular powder diffraction using single-photon-counting strip detectors: high-resolution structure of the pharmaceutical peptide octreotide. ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES 2021; 77:186-195. [PMID: 33944797 DOI: 10.1107/s2053273321001698] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 02/11/2021] [Indexed: 11/10/2022]
Abstract
Advances in instrumentation, as well as the development of powerful crystallographic software have significantly facilitated the collection of high-resolution diffraction data and have made X-ray powder diffraction (XRPD) particularly useful for the extraction of structural information; this is true even for complex molecules, especially when combined with synchrotron radiation. In this study, in-line with past instrumental profile studies, an improved data collection strategy exploiting the MYTHEN II detector system together with significant beam focusing and tailored data collection options was introduced and optimized for protein samples at the Material Science beamline at the Swiss Light Source. Polycrystalline precipitates of octreotide, a somatostatin analog of particular pharmaceutical interest, were examined with this novel approach. XRPD experiments resulted in high angular and d-spacing (1.87 Å) resolution data, from which electron-density maps of enhanced quality were extracted, revealing the molecule's structural properties. Since microcrystalline precipitates represent a viable alternative for administration of therapeutic macromolecules, XRPD has been acknowledged as the most applicable tool for examining a wide spectrum of physicochemical properties of such materials and performing studies ranging from phase identification to complete structural characterization.
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Affiliation(s)
- Maria Spiliopoulou
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
| | - Fotini Karavassili
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
| | | | - Alexandros Valmas
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
| | - Stavroula Fili
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
| | - Christos Kosinas
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
| | | | | | - Mickael Morin
- Excelsus Structural Solutions (Swiss) AG, Park Innovaare, Villigen, 5234, Switzerland
| | | | - Fabia Gozzo
- Excelsus Structural Solutions (Swiss) AG, Park Innovaare, Villigen, 5234, Switzerland
| | - Irene Margiolaki
- Department of Biology, Section of Genetics, Cell Biology and Development, University of Patras, Patras, GR-26500, Greece
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4
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Shen J. D-Amino acid substituted peptides as potential alternatives of homochiral L-configurations. Amino Acids 2021; 53:265-280. [PMID: 33537892 DOI: 10.1007/s00726-021-02947-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 01/22/2021] [Indexed: 11/28/2022]
Abstract
On the primitive Earth, both L- and D-amino acids would have been present. However, only L-amino acids are essential blocks to construct proteins in modern life. To study the relative stability of D-amino acid substituted peptides, a variety of computational methods were applied. Ten prebiotic amino acids (Gly, Ala, Asp, Glu, Ile, Leu, Pro, Ser, Thr, and Val) were previously determined by multiple meteorite, spark discharge, and hydrothermal vent studies. Some previously reported early Earth polypeptide analogs were focused on in this study. Tripeptides composed of only Asp, Ser, and Val exemplified that different positions (i.e., N-terminus, C-terminus, and middle) made a difference in the minimal folding energy of peptides, while the chemical classification of amino acid (hydrophobic, acidic, or hydroxylic) did not show a significant difference. Hierarchical cluster analysis for dipeptides with all possible combinations of the proposed ten prebiotic amino acids and their D-amino acid substituted derivatives generated five clusters. Primordial simple polypeptides were modeled to test the significance of molecular fluctuations, secondary structure occupancies, and folding energy differences based on these clusters. We found peptides with α-helices, long β-sheets, and long loops are usually less sensitive to D-amino acid replacements in comparison to short β-sheets. Intriguingly, amongst 129 D-amino acid residues, mutation sensitivity profiles presented that the ratio of more to less stable residues was about 1. In conclusion, some combinations of a mixture of L- and D-amino acids can potentially act as essential building blocks of life.
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Affiliation(s)
- Jianxun Shen
- School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, St Andrews, KY16 9AL, UK.
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5
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Liu L, Gellman SH. Harnessing Noncovalent Interactions to Drive Single-Chain Nanoparticle Formation. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lei Liu
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - Samuel H. Gellman
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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6
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Vasquez JK, West KHJ, Yang T, Polaske TJ, Cornilescu G, Tonelli M, Blackwell HE. Conformational Switch to a β-Turn in a Staphylococcal Quorum Sensing Signal Peptide Causes a Dramatic Increase in Potency. J Am Chem Soc 2020; 142:750-761. [PMID: 31859506 DOI: 10.1021/jacs.9b05513] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report the solution-phase structures of native signal peptides and related analogs capable of either strongly agonizing or antagonizing the AgrC quorum sensing (QS) receptor in the emerging pathogen Staphylococcus epidermidis. Chronic S. epidermidis infections are often recalcitrant to traditional therapies due to antibiotic resistance and formation of robust biofilms. The accessory gene regulator (agr) QS system plays an important role in biofilm formation in this opportunistic pathogen, and the binding of an autoinducing peptide (AIP) signal to its cognate transmembrane receptor (AgrC) is responsible for controlling agr. Small molecules or peptides capable of modulating this binding event are of significant interest as probes to investigate both the agr system and QS as a potential antivirulence target. We used NMR spectroscopy to characterize the structures of the three native S. epidermidis AIP signals and five non-native analogs with distinct activity profiles in the AgrC-I receptor from S. epidermidis. These studies revealed a suite of structural motifs critical for ligand activity. Interestingly, a unique β-turn was present in the macrocycles of the two most potent AgrC-I modulators, in both an agonist and an antagonist, which was distinct from the macrocycle conformation in the less-potent AgrC-I modulators and in the native AIP-I itself. This previously unknown β-turn provides a structural rationale for these ligands' respective biological activity profiles. Development of analogs to reinforce the β-turn resulted in our first antagonist with subnanomolar potency in AgrC-I, while analogs designed to contain a disrupted β-turn were dramatically less potent relative to their parent compounds. Collectively, these studies provide new insights into the AIP:AgrC interactions crucial for QS activation in S. epidermidis and advance the understanding of QS at the molecular level.
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Affiliation(s)
- Joseph K Vasquez
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Korbin H J West
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Tian Yang
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Thomas J Polaske
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Gabriel Cornilescu
- National Magnetic Resonance Facility at Madison , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Helen E Blackwell
- Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
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7
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Weidmann J, Schnölzer M, Dawson PE, Hoheisel JD. Copying Life: Synthesis of an Enzymatically Active Mirror-Image DNA-Ligase Made of D-Amino Acids. Cell Chem Biol 2019; 26:645-651.e3. [PMID: 30880154 DOI: 10.1016/j.chembiol.2019.02.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 11/27/2018] [Accepted: 02/07/2019] [Indexed: 11/17/2022]
Abstract
Our objective is the creation of a mirror-image synthetic biology: that is, to mimic, entirely independent of Nature, a biological system and to re-create it from artificial component parts. Utilizing enantiomeric L-nucleotides and D-amino acids rather than the natural components, we use chemical synthesis toward a basic, self-replicating mirror-image biological system. Here, we report the synthesis of a functional DNA-ligase in the D-enantiomeric conformation, which is an exact mirror-image of the natural enzyme, exhibiting DNA ligation activity on chirally inverted nucleic acids in L-conformation, but not acting on natural substrates and with natural co-factors. Starting from the known structure of the Paramecium bursaria chlorella virus 1 DNA-ligase and the homologous but shorter DNA-ligase of Haemophilus influenza, we designed and synthesized chemically peptides, which could then be assembled into a full-length molecule yielding a functional protein. The structure and the activity of the mirror-image ligase were characterized, documenting its enantiospecific functionality.
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Affiliation(s)
- Joachim Weidmann
- Functional Genome Analysis, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, 69120 Heidelberg, Germany; Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Martina Schnölzer
- Functional Proteome Analysis, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
| | - Philip E Dawson
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jörg D Hoheisel
- Functional Genome Analysis, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
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8
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Childers MC, Towse CL, Daggett V. Molecular dynamics-derived rotamer libraries for d-amino acids within homochiral and heterochiral polypeptides. Protein Eng Des Sel 2018; 31:191-204. [PMID: 29992252 PMCID: PMC6205366 DOI: 10.1093/protein/gzy016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 06/15/2018] [Indexed: 01/06/2023] Open
Abstract
Computational resources have contributed to the design and engineering of novel proteins by integrating genomic, structural and dynamic aspects of proteins. Non-canonical amino acids, such as d-amino acids, expand the available sequence space for designing and engineering proteins; however, the rotamer libraries for d-amino acids are usually constructed as the mirror images of l-amino acid rotamer libraries, an assumption that has not been tested. To this end, we have performed molecular dynamics (MD) simulations of model host-guest peptide systems containing d-amino acids. Our simulations systematically address the applicability of the mirror image convention as well as the effects of neighboring residue chirality. Rotamer libraries derived from these systems provide realistic rotamer distributions suitable for use in both rational and computational design workflows. Our simulations also address the impact of chirality on the intrinsic conformational preferences of amino acids, providing fundamental insights into the relationship between chirality and biomolecular dynamics. While d-amino acids are rare in naturally occurring proteins, they are used in designed proteins to stabilize a desired conformation, increase bioavailability or confer favorable biochemical and physical attributes. Here, we present d-amino acid rotamer libraries derived from MD simulations of alanine-based host-guest pentapeptides and show how certain residues can deviate from mirror image symmetry. Our simulations directly model d-amino acids as guest residues within the chiral l-Ala and d-Ala pentapeptide series to explicitly incorporate any contributions resulting from the chiralities of neighboring residues.
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Affiliation(s)
| | - Clare-Louise Towse
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Valerie Daggett
- Department of Bioengineering, University of Washington, Seattle, WA, USA
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9
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Mong SK, Cochran FV, Yu H, Graziano Z, Lin YS, Cochran JR, Pentelute BL. Heterochiral Knottin Protein: Folding and Solution Structure. Biochemistry 2017; 56:5720-5725. [PMID: 28952732 DOI: 10.1021/acs.biochem.7b00722] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Homochirality is a general feature of biological macromolecules, and Nature includes few examples of heterochiral proteins. Herein, we report on the design, chemical synthesis, and structural characterization of heterochiral proteins possessing loops of amino acids of chirality opposite to that of the rest of a protein scaffold. Using the protein Ecballium elaterium trypsin inhibitor II, we discover that selective β-alanine substitution favors the efficient folding of our heterochiral constructs. Solution nuclear magnetic resonance spectroscopy of one such heterochiral protein reveals a homogeneous global fold. Additionally, steered molecular dynamics simulation indicate β-alanine reduces the free energy required to fold the protein. We also find these heterochiral proteins to be more resistant to proteolysis than homochiral l-proteins. This work informs the design of heterochiral protein architectures containing stretches of both d- and l-amino acids.
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Affiliation(s)
- Surin K Mong
- Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Frank V Cochran
- Department of Bioengineering, Stanford University , 450 Serra Mall, Stanford, California 94305, United States
| | - Hongtao Yu
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Zachary Graziano
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Yu-Shan Lin
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States
| | - Jennifer R Cochran
- Department of Bioengineering, Stanford University , 450 Serra Mall, Stanford, California 94305, United States
| | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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10
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Lubecka EA, Liwo A. A general method for the derivation of the functional forms of the effective energy terms in coarse-grained energy functions of polymers. II. Backbone-local potentials of coarse-grained O1→4-bonded polyglucose chains. J Chem Phys 2017; 147:115101. [DOI: 10.1063/1.4994130] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Affiliation(s)
- Emilia A. Lubecka
- Institute of Informatics, University of Gdańsk, Wita Stwosza 57, 80-308 Gdańsk, Poland
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Adam Liwo
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
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11
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Bakail M, Ochsenbein F. Targeting protein–protein interactions, a wide open field for drug design. CR CHIM 2016. [DOI: 10.1016/j.crci.2015.12.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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12
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Enantiomeric CopA3 dimer peptide suppresses cell viability and tumor xenograft growth of human gastric cancer cells. Tumour Biol 2015; 37:3237-45. [DOI: 10.1007/s13277-015-4162-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 09/27/2015] [Indexed: 10/23/2022] Open
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13
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Towse CL, Hopping G, Vulovic I, Daggett V. Nature versus design: the conformational propensities of D-amino acids and the importance of side chain chirality. Protein Eng Des Sel 2014; 27:447-55. [PMID: 25233851 PMCID: PMC4204638 DOI: 10.1093/protein/gzu037] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 08/04/2014] [Accepted: 08/11/2014] [Indexed: 11/12/2022] Open
Abstract
D-amino acids are useful building blocks for de novo peptide design and they play a role in aging-related diseases associated with gradual protein racemization. For amino acids with achiral side chains, one should be able to presume that the conformational propensities of L- and D-amino acids are a reflection of one another due to the straightforward geometric inversion at the Cα atom. However, this presumption does not account for the directionality of the backbone dipole and the inverted propensities have never been definitively confirmed in this context. Furthermore, there is little known of how alternative side chain chirality affects the backbone conformations of isoleucine and threonine. Using a GGXGG host-guest pentapeptide system, we have completed exhaustive sampling of the conformational propensities of the D-amino acids, including D-allo-isoleucine and D-allo-threonine, using atomistic molecular dynamics simulations. Comparison of these simulations with the same systems hosting the cognate L-amino acids verifies that the intrinsic backbone conformational propensities of the D-amino acids are the inverse of their cognate L-enantiomers. Where amino acids have a chiral center in their side chain (Thr, Ile) the β-configuration affects the backbone sampling, which in turn can confer different biological properties.
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Affiliation(s)
- Clare-Louise Towse
- Department of Bioengineering, University of Washington, Seattle, WA 98195-5013, USA
| | - Gene Hopping
- Department of Bioengineering, University of Washington, Seattle, WA 98195-5013, USA
| | - Ivan Vulovic
- Department of Bioengineering, University of Washington, Seattle, WA 98195-5013, USA
| | - Valerie Daggett
- Department of Bioengineering, University of Washington, Seattle, WA 98195-5013, USA
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14
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Ion channel stability of Gramicidin A in lipid bilayers: Effect of hydrophobic mismatch. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:328-38. [DOI: 10.1016/j.bbamem.2013.10.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 09/20/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022]
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15
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Sieradzan AK, Hansmann UH, Scheraga HA, Liwo A. Extension of UNRES force field to treat polypeptide chains with D-amino-acid residues. J Chem Theory Comput 2012; 8:4746-4757. [PMID: 24729761 PMCID: PMC3982868 DOI: 10.1021/ct3005563] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Coarse-grained force fields for protein simulations are usually designed and parameterized to treat proteins composed of natural L-amino-acid residues. However, D-amino-acid residues occur in bacterial, fungal (e.g., gramicidins), as well as human-designed proteins. For this reason, we have extended the UNRES coarse-grained force field developed in our laboratory to treat systems with D-amino-acid residues. We developed the respective virtual-bond-torsional and double-torsional potentials for rotation about the C α · · · C α virtual-bond axis and two consecutive C α · · · C α virtual-bond axes, respectively, as functions of virtual-bond-dihedral angles γ. In turn, these were calculated as potentials of mean force (PMFs) from the diabatic energy surfaces of terminally-blocked model compounds for glycine, alanine, and proline. The potential-energy surfaces were calculated by using the ab initio method of molecular quantum mechanics at the Møller-Plesset (MP2) level of theory and the 6-31G(d,p) basis set, with the rotation angles of the peptide groups about [Formula: see text] and [Formula: see text] used as variables, and the energy was minimized with respect to the remaining degrees of freedom. The PMFs were calculated by numerical integration for all pairs and triplets with all possible combinations of types (glycine, alanine, and proline) and chirality (D or L); however, symmetry relations reduce the number of non-equivalent torsional potentials to 13 and the number of double-torsional potentials to 63 for a given C-terminal blocking group. Subsequently, one- (for torsional) and two-dimensional (for double-torsional potentials) Fourier series were fitted to the PMFs to obtain analytical expressions. It was found that the torsional potentials of the x-Y and X-y types, where X and Y are Ala or Pro, respectively, and a lowercase letter denotes D-chirality, have global minima for small absolute values of γ, accounting for the double-helical structure of gramicidin A, which is a dimer of two chains, each possessing an alternating D-Tyr-L-Tyr sequence, and similar peptides. The side-chain and correlation potentials for D-amino-acid residues were obtained by applying the reflection about the [Formula: see text] plane to the respective potentials for the L-amino-acid residues.
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Affiliation(s)
- Adam K. Sieradzan
- Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
- Department of Chemistry and Biochemistry, Oklahoma University, Norman, OK, 73019, U.S.A
| | - Ulrich H.E. Hansmann
- Department of Chemistry and Biochemistry, Oklahoma University, Norman, OK, 73019, U.S.A
| | - Harold A. Scheraga
- Baker Laboratory of Chemistry and Chemical Biology, Cornell University, Ithaca, N.Y., 14853-1301, U.S.A
| | - Adam Liwo
- Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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16
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Gfeller D, Michielin O, Zoete V. SwissSidechain: a molecular and structural database of non-natural sidechains. Nucleic Acids Res 2012; 41:D327-32. [PMID: 23104376 PMCID: PMC3531096 DOI: 10.1093/nar/gks991] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Amino acids form the building blocks of all proteins. Naturally occurring amino acids are restricted to a few tens of sidechains, even when considering post-translational modifications and rare amino acids such as selenocysteine and pyrrolysine. However, the potential chemical diversity of amino acid sidechains is nearly infinite. Exploiting this diversity by using non-natural sidechains to expand the building blocks of proteins and peptides has recently found widespread applications in biochemistry, protein engineering and drug design. Despite these applications, there is currently no unified online bioinformatics resource for non-natural sidechains. With the SwissSidechain database (http://www.swisssidechain.ch), we offer a central and curated platform about non-natural sidechains for researchers in biochemistry, medicinal chemistry, protein engineering and molecular modeling. SwissSidechain provides biophysical, structural and molecular data for hundreds of commercially available non-natural amino acid sidechains, both in l- and d-configurations. The database can be easily browsed by sidechain names, families or physico-chemical properties. We also provide plugins to seamlessly insert non-natural sidechains into peptides and proteins using molecular visualization software, as well as topologies and parameters compatible with molecular mechanics software.
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Affiliation(s)
- David Gfeller
- Swiss Institute of Bioinformatics (SIB), Quartier Sorge, Bâtiment Génopode, CH-1015 Lausanne, Switzerland
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17
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Turpin ER, Hirst JD. Transformation of the dihedral corrective map for d-amino residues using the CHARMM force field. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.06.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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18
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Zhao L, Ericksen B, Wu X, Zhan C, Yuan W, Li X, Pazgier M, Lu W. Invariant gly residue is important for α-defensin folding, dimerization, and function: a case study of the human neutrophil α-defensin HNP1. J Biol Chem 2012; 287:18900-12. [PMID: 22496447 DOI: 10.1074/jbc.m112.355255] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The human α-defensins (HNP) are synthesized in vivo as inactive prodefensins, and contain a conserved glycine, Gly(17), which is part of a β-bulge structure. It had previously been shown that the glycine main chain torsion angles are in a D-configuration, and that d-amino acids but not L-alanine could be substituted at that position to yield correctly folded peptides without the help of a prodomain. In this study, the glycine to L-alanine mutant defensin was synthesized in the form of a prodefensin using native chemical ligation. The ligation product folded correctly and yielded an active peptide upon CNBr cleavage. The L-Ala(17)-HNP1 crystal structure depicted a β-bulge identical to wild-type HNP1. However, dimerization was perturbed, causing one monomer to tilt with respect to the other in a dimerization model. Inhibitory activity against the anthrax lethal factor showed a 2-fold reduction relative to wild-type HNP1 as measured by the inhibitory concentration IC(50). Self-association was slightly reduced, as detected by surface plasmon resonance measurements. According to the results of the virtual colony count assay, the antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus cereus exhibited a less than 2-fold reduction in virtual lethal dose values. Prodefensins with two other L-amino acid substitutions, Arg and Phe, at the same position did not fold, indicating that only small side chains are tolerable. These results further elucidate the factors governing the region of the β-bulge structure that includes Gly(17), illuminating why glycine is conserved in all mammalian α-defensins.
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Affiliation(s)
- Le Zhao
- The 1st Affiliated Hospital, Xi'an Jiaotong University School of Medicine, China
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19
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Sikorska E, Sobolewski D, Kwiatkowska A. Conformational preferences of proline derivatives incorporated into vasopressin analogues: NMR and molecular modelling studies. Chem Biol Drug Des 2012; 79:535-47. [PMID: 22226070 DOI: 10.1111/j.1747-0285.2012.01318.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, arginine vasopressin analogues modified with proline derivatives - indoline-2-carboxylic acid (Ica), (2S,4R)-4-(naphthalene-2-ylmethyl)pyrrolidine-2-carboxylic acid (Nmp), (2S,4S)-4-aminopyroglutamic acid (APy) and (2R,4S)-4-aminopyroglutamic acid, (Apy) - were examined using NMR spectroscopy and molecular modelling methods. The results have shown that Ica is involved in the formation of the cis peptide bond. Moreover, it reduces to a great extent the conformational flexibility of the peptide. In turn, incorporation of (2S,4R)-Nmp stabilizes the backbone conformation, which is heavily influenced by the pyrrolidine ring. However, the aromatic part of the Nmp side chain exhibits a high degree of conformational freedom. With analogues IV and V, introduction of the 4-aminopyroglumatic acid reduces locally conformational space of the peptides, but it also results in weaker interactions with the dodecylphosphocholine/sodium dodecyl sulphate micelle. Admittedly, both analogues are adsorbed on the micelle's surface but they do not penetrate into its core. With analogue V, the interactions between the peptide and the micelle seem to be so weak that conformational equilibrium is established between different bound states.
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Affiliation(s)
- Emilia Sikorska
- Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland.
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20
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Rodriguez-Granillo A, Annavarapu S, Zhang L, Koder RL, Nanda V. Computational design of thermostabilizing D-amino acid substitutions. J Am Chem Soc 2011; 133:18750-9. [PMID: 21978298 PMCID: PMC3443866 DOI: 10.1021/ja205609c] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Judicious incorporation of D-amino acids in engineered proteins confers many advantages such as preventing degradation by endogenous proteases and promoting novel structures and functions not accessible to homochiral polypeptides. Glycine to D-alanine substitutions at the carboxy termini can stabilize α-helices by reducing conformational entropy. Beyond alanine, we propose additional side chain effects on the degree of stabilization conferred by D-amino acid substitutions. A detailed, molecular understanding of backbone and side chain interactions is important for developing rational, broadly applicable strategies in using D-amino acids to increase protein thermostability. Insight from structural bioinformatics combined with computational protein design can successfully guide the selection of stabilizing D-amino acid mutations. Substituting a key glycine in the Trp-cage miniprotein with D-Gln dramatically stabilizes the fold without altering the protein backbone. Stabilities of individual substitutions can be understood in terms of the balance of intramolecular forces both at the α-helix C-terminus and throughout the protein.
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Affiliation(s)
- Agustina Rodriguez-Granillo
- Department of Biochemistry, Robert Wood Johnson Medical School, UMDNJ and the Center for Advanced Biotechnology and Medicine, Piscataway, New Jersey 08854
| | - Srinivas Annavarapu
- Department of Biochemistry, Robert Wood Johnson Medical School, UMDNJ and the Center for Advanced Biotechnology and Medicine, Piscataway, New Jersey 08854
| | - Lei Zhang
- Department of Physics, The City College of New York, New York, New York 10031
| | - Ronald L. Koder
- Department of Physics, The City College of New York, New York, New York 10031
| | - Vikas Nanda
- Department of Biochemistry, Robert Wood Johnson Medical School, UMDNJ and the Center for Advanced Biotechnology and Medicine, Piscataway, New Jersey 08854
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21
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Turpin ER, Bonev BB, Hirst JD. Stereoselective disulfide formation stabilizes the local peptide conformation in nisin mimics. Biochemistry 2011; 49:9594-603. [PMID: 20882989 DOI: 10.1021/bi101214t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nisin is a polymacrocyclic peptide antimicrobial with high activity against Gram-positive bacteria. Lanthionine and methyllanthionine bridges, closing the macrocycles, are stabilized by thioether bonds, formed between cysteines and dehydrated serine or threonine. The role of polypeptide backbone conformation in the formation of macrocycles A and B within cysteine mutants of nisin residues 1−12 is investigated here by molecular dynamics simulations. Enantiomeric combinational space of Cys3 and Cys7 and of Cys8 and Cys11 is examined for the preference of disulfide bond formation over helical turn formation within this region. A clear preference for spontaneous disulfide formation and closure of rings 3,7 and 8,11 is demonstrated for the D-Cys3, D-Cys7, L-Cys8, L-Cys11 nisin homologue, while interlinked rings A and B are obtained through disulfide bridges between L-Cys3 and D-Cys8 and between D-Cys7 and D-Cys11. This study offers a simple designer approach to solid phase synthesis of macrocyclic peptides and lantibiotic analogues.
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22
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Elaboration of antibiofilm materials by chemical grafting of an antimicrobial peptide. Appl Microbiol Biotechnol 2010; 89:623-34. [DOI: 10.1007/s00253-010-2930-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 10/01/2010] [Accepted: 10/01/2010] [Indexed: 10/19/2022]
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23
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Friedman M. Origin, Microbiology, Nutrition, and Pharmacology of D-Amino Acids. Chem Biodivers 2010; 7:1491-530. [DOI: 10.1002/cbdv.200900225] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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24
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Kantharaju, Raghothama S, Aravinda S, Shamala N, Balaram P. Helical conformations of hexapeptides containing N-terminus diproline segments. Biopolymers 2010; 94:360-70. [DOI: 10.1002/bip.21395] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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25
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Annavarapu S, Nanda V. Mirrors in the PDB: left-handed alpha-turns guide design with D-amino acids. BMC STRUCTURAL BIOLOGY 2009; 9:61. [PMID: 19772623 PMCID: PMC2759939 DOI: 10.1186/1472-6807-9-61] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Accepted: 09/22/2009] [Indexed: 11/28/2022]
Abstract
Background Incorporating variable amino acid stereochemistry in molecular design has the potential to improve existing protein stability and create new topologies inaccessible to homochiral molecules. The Protein Data Bank has been a reliable, rich source of information on molecular interactions and their role in protein stability and structure. D-amino acids rarely occur naturally, making it difficult to infer general rules for how they would be tolerated in proteins through an analysis of existing protein structures. However, protein elements containing short left-handed turns and helices turn out to contain useful information. Molecular mechanisms used in proteins to stabilize left-handed elements by L-amino acids are structurally enantiomeric to potential synthetic strategies for stabilizing right-handed elements with D-amino acids. Results Propensities for amino acids to occur in contiguous αL helices correlate with published thermodynamic scales for incorporation of D-amino acids into αR helices. Two backbone rules for terminating a left-handed helix are found: an αR conformation is disfavored at the amino terminus, and a βR conformation is disfavored at the carboxy terminus. Helix capping sidechain-backbone interactions are found which are unique to αL helices including an elevated propensity for L-Asn, and L-Thr at the amino terminus and L-Gln, L-Thr and L-Ser at the carboxy terminus. Conclusion By examining left-handed α-turns containing L-amino acids, new interaction motifs for incorporating D-amino acids into right-handed α-helices are identified. These will provide a basis for de novo design of novel heterochiral protein folds.
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Affiliation(s)
- Srinivas Annavarapu
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA.
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26
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Peacock A, Stuckey J, Pecoraro V. Switching the Chirality of the Metal Environment Alters the Coordination Mode in Designed Peptides. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200902166] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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27
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Punitha V, Raman SS, Parthasarathi R, Subramanian V, Rao JR, Nair BU, Ramasami T. Molecular dynamics investigations on the effect of D amino acid substitution in a triple-helix structure and the stability of collagen. J Phys Chem B 2009; 113:8983-92. [PMID: 19518060 DOI: 10.1021/jp808690m] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies on the structure and stability of peptides and proteins during l-->d configurational change are certainly important for the designing of peptides with new biological activity and protein engineering. The l-->d amino acid (d AA) changes have been observed in aged proteins such as collagen. Hence, in this study, an attempt has been made to explore the effect of the replacement of l amino acid (l AA) in the model collagen-like peptides with d AA and the origin of structural stability (destability) has been traced using the molecular dynamics (MD) method employing the AMBER force field. Our results reveal that the substitution of d AA produces a large local disruption to the triple-helical structure. Formation of a kink (bulge) at the site of substitution is observed from the detailed analysis of MD trajectory. However, this local perturbation of kinked helix changes the direction of the helices and affects the relative orientation of the respective AA residues for helix-helix interaction, enough to affect the overall stability of the model collagen-like peptide. The destabilization energy per d Ala substitution is 7.87 kcal/mol, which is similar to the value for the Gly-->Ala mutation in collagen. Since the Gly-->Ala mutation is involved in genetic disorders such as osteogenesis imperfecta (OI), the l-->d configurational change may produce a similar effect on collagen.
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Affiliation(s)
- V Punitha
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific Industrial Research, Sardar Patel Road, Adyar, Chennai 600 020, India
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28
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Yongye AB, Li Y, Giulianotti MA, Yu Y, Houghten RA, Martínez-Mayorga K. Modeling of peptides containing D-amino acids: implications on cyclization. J Comput Aided Mol Des 2009; 23:677-89. [PMID: 19593648 DOI: 10.1007/s10822-009-9295-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 06/25/2009] [Indexed: 11/25/2022]
Abstract
Cyclic peptides are therapeutically attractive due to their high bioavailability, potential selectivity, and scaffold novelty. Furthermore, the presence of D-residues induces conformational preferences not followed by peptides consisting of naturally abundant L-residues. Therefore, comprehending how amino acids induce turns in peptides, subsequently facilitating cyclization, is significant in peptide design. Here, we performed 20-ns explicit-solvent molecular dynamics simulations for three diastereomeric peptides with stereochemistries: LLLLL, LLLDL, and LDLDL. Experimentally LLLLL and LDLDL readily cyclize, whereas LLLDL cyclizes in low yield. Simulations at 310 K produced conformations with inter-terminal hydrogen bonds that correlated qualitatively with the experimental cyclization trend. Energies obtained for representative structures from quantum chemical (B3LYP/PCM/cc-pVTZ//HF/6-31G*) calculations predicted pseudo-cyclic and extended conformations as the most stable for LLLLL and LLLDL, respectively, in agreement with the experimental data. In contrast, the most stable conformer predicted for peptide LDLDL was not a pseudo-cyclic structure. Moreover, D-residues preferred the experimentally less populated alpha(L) rotamers even when simulations were performed at a higher temperature and with strategically selected starting conformations. Energies calculated with molecular mechanics were consistent only with peptide LLLLL. Thus, the conformational preferences obtained for the all L: -amino acid peptide were in agreement with the experimental observations. Moreover, refinement of the force field is expected to provide far-reaching conformational sampling of peptides containing D-residues to further develop force field-based conformational-searching methods.
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Affiliation(s)
- Austin B Yongye
- Torrey Pines Institute for Molecular Studies, Port Saint Lucie, FL 34987, USA
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29
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Peacock AFA, Stuckey JA, Pecoraro VL. Switching the chirality of the metal environment alters the coordination mode in designed peptides. Angew Chem Int Ed Engl 2009; 48:7371-4. [PMID: 19579245 PMCID: PMC3014729 DOI: 10.1002/anie.200902166] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effects of switching the chirality of a single layer of amino acids in a three stranded coiled coil has been investigated. X-ray crystallography reveals that this modification is well tolerated and does not alter the designed structure. In contrast, spectroscopic studies of cadmium binding to both the L- and D- enantiomers of the penicillamine, provide evidence that this switch dramatically alters the metal binding capability, the resulting coordination environment and the position of binding.
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Affiliation(s)
- Anna F. A. Peacock
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109 (USA)
| | - Jeanne A. Stuckey
- Life Sciences Institute, University and Michigan, Ann Arbor, MI 48109 (USA)
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30
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Mohammad MM, Movileanu L. Excursion of a single polypeptide into a protein pore: simple physics, but complicated biology. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:913-25. [PMID: 18368402 DOI: 10.1007/s00249-008-0309-9] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 01/04/2008] [Accepted: 03/10/2008] [Indexed: 10/22/2022]
Abstract
Despite its fundamental and critical importance in molecular biology and practical medical biotechnology, how a polypeptide interacts with a transmembrane protein pore is not yet comprehensively understood. Here, we employed single-channel electrical recordings to reveal the interactions of short polypeptides and small folded proteins with a robust beta-barrel protein pore. The short polypeptides were approximately 25 residues in length, resembling positively charged targeting presequences involved in protein import. The proteins were consisted of positively charged pre-cytochrome b2 fragments (pb2) fused to the small ribonuclease barnase (approximately 110 residues, Ba). Single-molecule experiments exploring the interaction of a folded pb2-Ba protein with a single beta-barrel pore, which contained negatively charged electrostatic traps, revealed the complexity of a network of intermolecular forces, including driving and electrostatic ones. In addition, the interaction was dependent on other factors, such as the hydrophobic content of the interacting polypeptide, the location of the electrostatic trap, the length of the pb2 presequence and temperature. This single-molecule approach together with protein design of either the interacting polypeptide or the pore lumen opens new opportunities for the exploration of the polypeptide-pore interaction at high temporal resolution. Such future studies are also expected to unravel the advantages and limitations of the nanopore technique for the detection and exploration of individual polypeptides.
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Affiliation(s)
- Mohammad M Mohammad
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244-1130, USA
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31
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Abstract
PURPOSE OF REVIEW To review the role of chirality in current ocular pharmacology. The importance of stereo-isomeric purity has frequently been emphasized in recent years. Development of chirally pure medications can lead to improved efficacy and side-effect profiles. Practitioners prescribing ocular agents may benefit from understanding the effects of chirality in their evaluation of old and new medications. RECENT FINDINGS Chirality can affect multiple classes of ocular agents. Although the ways in which stereo-isomers influence the properties of a drug differ, this review illustrates the benefit of knowledge of individual isomers' effects in clinical decision making. The variety of possible effects stereo-isomers produce further underlines the importance of purification and in-depth analysis of chiral compounds. SUMMARY Many important agents exist as a mixture of two different stereoisomers. Both isomers may produce a pharmacological effect; however, these effects may be different from one another and one isomer may even give a result opposite from the desired pharmacological effect. Here we examine published findings on ocular medications relating to their chiral nature and summarize the possible ways chirality affects the activity of a few ocular agents. Many more ocular medications have not been investigated to ascertain their chiral properties. This review adds to the recent emphasis on investigating stereo-isomers for individual selectivity of beneficial and adverse profiles.
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Affiliation(s)
- Andrey Leonov
- UMDNJ - New Jersey Medical School, Newark, NJ 07103, USA
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32
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Kelkar DA, Chattopadhyay A. The gramicidin ion channel: A model membrane protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2011-25. [PMID: 17572379 DOI: 10.1016/j.bbamem.2007.05.011] [Citation(s) in RCA: 264] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 05/09/2007] [Accepted: 05/10/2007] [Indexed: 02/07/2023]
Abstract
The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization, dynamics and function of membrane-spanning channels. In recent times, the availability of crystal structures of complex ion channels has challenged the role of gramicidin as a model membrane protein and ion channel. This review focuses on the suitability of gramicidin as a model membrane protein in general, and the information gained from gramicidin to understand lipid-protein interactions in particular. Special emphasis is given to the role and orientation of tryptophan residues in channel structure and function and recent spectroscopic approaches that have highlighted the organization and dynamics of the channel in membrane and membrane-mimetic media.
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Affiliation(s)
- Devaki A Kelkar
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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33
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Liu D, Madani N, Li Y, Cao R, Choi WT, Kawatkar SP, Lim MY, Kumar S, Dong CZ, Wang J, Russell JD, Lefebure CR, An J, Wilson S, Gao YG, Pallansch LA, Sodroski JG, Huang Z. Crystal structure and structural mechanism of a novel anti-human immunodeficiency virus and D-amino acid-containing chemokine. J Virol 2007; 81:11489-98. [PMID: 17686848 PMCID: PMC2045531 DOI: 10.1128/jvi.02845-06] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Chemokines and their receptors play important roles in normal physiological functions and the pathogeneses of a wide range of human diseases, including the entry of human immunodeficiency virus type 1 (HIV-1). However, the use of natural chemokines to probe receptor biology or to develop therapeutic drugs is limited by their lack of selectivity and the poor understanding of mechanisms in ligand-receptor recognition. We addressed these issues by combining chemical and structural biology in research into molecular recognition and inhibitor design. Specifically, the concepts of chemical biology were used to develop synthetically and modularly modified (SMM) chemokines that are unnatural and yet have properties improved over those of natural chemokines in terms of receptor selectivity, affinity, and the ability to explore receptor functions. This was followed by using structural biology to determine the structural basis for synthetically perturbed ligand-receptor selectivity. As a proof-of-principle for this combined chemical and structural-biology approach, we report a novel D-amino acid-containing SMM-chemokine designed based on the natural chemokine called viral macrophage inflammatory protein II (vMIP-II). The incorporation of unnatural D-amino acids enhanced the affinity of this molecule for CXCR4 but significantly diminished that for CCR5 or CCR2, thus yielding much more selective recognition of CXCR4 than wild-type vMIP-II. This D-amino acid-containing chemokine also showed more potent and specific inhibitory activity against HIV-1 entry via CXCR4 than natural chemokines. Furthermore, the high-resolution crystal structure of this D-amino acid-containing chemokine and a molecular-modeling study of its complex with CXCR4 provided the structure-based mechanism for the selective interaction between the ligand and chemokine receptors and the potent anti-HIV activity of D-amino acid-containing chemokines.
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Affiliation(s)
- Dongxiang Liu
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Zhou Y, Oostenbrink C, Jongejan A, Van Gunsteren WF, Hagen WR, De Leeuw SW, Jongejan JA. Computational study of ground-state chiral induction in small peptides: comparison of the relative stability of selected amino acid dimers and oligomers in homochiral and heterochiral combinations. J Comput Chem 2007; 27:857-67. [PMID: 16541426 DOI: 10.1002/jcc.20378] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The relative stabilities of homochiral and heterochiral forms of selected dipeptides, AA, AS, AC, AV, AF, AD, AK, tripeptides, AAA, AVA, and an acetylpentapeptide, AcGLSFA, have been calculated using thermodynamic integration protocols and the GROMOS 53A6 force field. Integration pathways have been designed that produce minimal disturbance to the system, including the use of soft atoms, low-energy intermediates, and chiral inversion of the smaller amino acid in the peptide. Comparison of the results obtained by thermodynamic integration between the diastereomeric forms (in explicit water, at 300 K) and from exhaustive global minimum-energy searches for the individual dipeptides (implicit water, epsilon = 78, 0 K) suggests that entropic contributions to the relative stability of the chiral forms are important. This conclusion is supported by the results of explicit calculation of the effect of temperature on the relative stability of alanylvalylalanine diastereomers. The Gibbs free energy calculations predict that at ambient temperature and pressure homochiral dipeptides with small side chains or polar groups in the vicinity of the peptide backbone, AA, AS, and AD, are more stable than their heterochiral counterparts by fractions of a kJ/mol. For bigger side chains, AC, AV, AF, and AK, the heterochiral diastereomers appear to be more stable. Predicted relative stabilities are in line with observations reported in the literature for AE and YY. Excellent agreement is found for the calculated and experimentally determined relative stabilities of the diastereomers of the dipeptide AA and of all-L AcGLSFA and its diastereomer containing D-serine in the central position. Addition of counterions to the solvent box has no significant effects on charged and neutral forms. From the present findings it would appear unlikely that the intrinsic stability difference between homo- and heterochiral dipeptides has been a driving force in a primordial selection process leading to the incorporation of amino acids with a single enantiomeric configuration in natural proteins.
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Affiliation(s)
- Yu Zhou
- Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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35
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Horng JC, Kotch FW, Raines RT. Is glycine a surrogate for a D-amino acid in the collagen triple helix? Protein Sci 2006; 16:208-15. [PMID: 17189476 PMCID: PMC2203290 DOI: 10.1110/ps.062560107] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Collagen is the most abundant protein in animals. Every third residue in a collagen strand is a glycine with phi, psi = -70 degrees, 175 degrees. A recent computational study suggested that replacing these glycine residues with D-alanine or D-serine would stabilize the collagen triple helix. This hypothesis is of substantial importance, as the glycine residues in collagen constitute nearly 10% of the amino acid residues in humans. To test this hypothesis, we synthesized a series of collagen mimic peptides that contain one or more D-alanine or D-serine residues replacing the canonical glycine residues. Circular dichroism spectroscopy and thermal denaturation experiments indicated clearly that the substitution of glycine with D-alanine or D-serine greatly disfavors the formation of a triple helix. Host-guest studies also revealed that replacing a single glycine residue with D-alanine is more destabilizing than is its replacement with L-alanine, a substitution that results from a common mutation in patients with collagen-related diseases. These data indicate that the glycine residues in collagen are not a surrogate for a D-amino acid and support the notion that the main-chain torsion angles of a glycine residue in the native structure (especially, phi > 0 degrees ) are critical determinants for its beneficial substitution with a D-amino acid in a protein.
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Affiliation(s)
- Jia-Cherng Horng
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA
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Franco A, Pisarewicz K, Moller C, Mora D, Fields GB, Marì F. Hyperhydroxylation: A New Strategy for Neuronal Targeting by Venomous Marine Molluscs. MOLLUSCS 2006; 43:83-103. [PMID: 17153339 DOI: 10.1007/978-3-540-30880-5_4] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Venomous marine molluscs belonging to the genus Conus (cone snails) utilize a unique neurochemical strategy to capture their prey. Their venom is composed of a complex mixture of highly modified peptides (conopeptides) that interact with a wide range of neuronal targets. In this chapter, we describe a set of modifications based upon the hydroxylation of polypeptidic chains that are defining within the neurochemical strategy used by cone snails to capture their prey. In particular, we present a differential hydroxylation strategy that affects the neuronal targeting of a new set of a-conotoxins, mini-M conotoxins, conophans, and y-hydroxyconophans. Differential hydroxylation, preferential hydroxylation and hyperhydroxylation have been observed in these conopeptide families as a means of augmenting the venom arsenal used by cone snails for neuronal targeting and prey capture.
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Affiliation(s)
- A Franco
- Department of Chemistry & Biochemistry, Centre of Excellence in Biomedical and Marine Biotechnology, Florida Atlantic University, 777 Glades Rd., Boca Raton, 33431 Florida, USA
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Auvynet C, Seddiki N, Dunia I, Nicolas P, Amiche M, Lacombe C. Post-translational amino acid racemization in the frog skin peptide deltorphin I in the secretion granules of cutaneous serous glands. Eur J Cell Biol 2005; 85:25-34. [PMID: 16373172 DOI: 10.1016/j.ejcb.2005.09.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 09/05/2005] [Accepted: 09/05/2005] [Indexed: 10/25/2022] Open
Abstract
The dermal glands of the South American hylid frog Phyllomedusa bicolor synthesize and expel huge amounts of cationic, alpha-helical, 24- to 33-residue antimicrobial peptides, the dermaseptins B. These glands also produce a wide array of peptides that are similar to mammalian hormones and neuropeptides, including a heptapeptide opioid containing a D-amino acid, deltorphin I (Tyr-DAla-Phe-Asp-Val-Val-Gly NH2). Its biological activity is due to the racemization of L-Ala2 to D-Ala. The dermaseptins B and deltorphins are all derived from a single family of precursor polypeptides that have an N-terminal preprosequence that is remarkably well conserved, although the progenitor sequences giving rise to mature opioid or antimicrobial peptides are markedly different. Monoclonal and polyclonal antibodies were used to examine the cellular and ultrastructural distributions of deltorphin I and dermaseptin B in the serous glands by immunofluoresence confocal microscopy and immunogold-electron microscopy. Preprodeltorphin I and preprodermaseptins B are sorted into the regulated pathway of secretion, where they are processed to give the mature products. Deltorphin I, [l-Ala2]-deltorphin I and dermaseptin B are all stored together in secretion granules which accumulate in the cytoplasm of all serous glands. We conclude that the L- to D-amino acid isomerization of the deltorphin I occurs in the secretory granules as a post-translational event. Thus the specificity of isomerization depends on the presence of structural and/or conformational determinants in the peptide N-terminus surrounding the isomerization site.
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Affiliation(s)
- Constance Auvynet
- Peptidome de la peau d'amphibiens, FRE 2852, CNRS-Université Paris-6, Tour 43, Institut Jacques Monod, 2 Place Jussieu, F-75251 Paris, Cedex 05, France
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Xie C, Prahl A, Ericksen B, Wu Z, Zeng P, Li X, Lu WY, Lubkowski J, Lu W. Reconstruction of the Conserved β-Bulge in Mammalian Defensins Using d-Amino Acids. J Biol Chem 2005; 280:32921-9. [PMID: 15894545 DOI: 10.1074/jbc.m503084200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Defensins are cationic antimicrobial mini-proteins that play important roles in the innate immune defense against microbial infection. Six invariant Cys residues in each defensin form three structurally indispensable intramolecular disulfide bridges. The only other residue invariant in all known mammalian defensins is a Gly. Structural studies indicate that the invariant Gly residue is located in an atypical, classic-type beta-bulge with the backbone torsion angles (Phi, Psi) disallowed for L-amino acids but permissible for D-enantiomers. We replaced the invariant Gly17 residue in human neutrophil alpha-defensin 2 (HNP2) by L-Ala or one of the D-amino acids Ala, Glu, Phe, Arg, Thr, Val, or Tyr. Although L-Ala17-HNP2 could not be folded, resulting in massive aggregation, all of the D-amino acid-substituted analogs folded with high efficiency. The high resolution x-ray crystal structures of dimeric D-Ala17-HNP2 were determined in three different crystal forms, showing a well preserved beta-bulge identical to those found in other defensins. The seven D-analogs of HNP2 exhibited highly variable bactericidal activity against Gram-positive and Gram-negative test strains, consistent with the premise that interplay between charge and hydrophobicity dictates how amphiphilic defensins kill. Further, the bactericidal activity of these d-amino acid analogs of HNP2 correlated well with their ability to induce leakage from large unilamellar vesicles, supporting membrane permeabilization as the lethal event in microbial killing by HNP2. Our findings identify a conformational prerequisite in the beta-bulge of defensins essential for correct folding and native structure, thereby explaining the molecular basis of the Gly-Xaa-Cys motif conserved in all mammalian defensins.
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Affiliation(s)
- Cao Xie
- Institute of Human Virology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA
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Sal-Man N, Gerber D, Shai Y. Hetero-assembly between all-L- and all-D-amino acid transmembrane domains: forces involved and implication for inactivation of membrane proteins. J Mol Biol 2005; 344:855-64. [PMID: 15533450 DOI: 10.1016/j.jmb.2004.09.066] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 09/22/2004] [Accepted: 09/23/2004] [Indexed: 11/28/2022]
Abstract
Protein-protein interactions within the membrane, partially or fully mediated by transmembrane (TM) domains, are involved in many vital cellular processes. Since the unique feature of the membrane environment enables protein-protein assembly that otherwise is not energetically favored in solution, the structural restrictions involved in the assembly of soluble proteins are not necessarily valid for the assembly of TM domains. Here we used the N-terminal TM domain (Tar-1) of the Escherichia coli aspartate receptor as a model system for examining the stereospecificity of TM-TM interactions in vitro and in vivo in isolated systems, and in the context of the full receptor. For this propose, we synthesized Tar-1 all-l and all-d amino acid TM peptides, a mutant TM peptide and an unrelated TM peptide. The data revealed: (i) Tar-1 all-d specifically associated with Tar-1 all-l within a model lipid membrane, as determined by using fluorescence energy transfer experiments; (ii) Tar-1 all-l and all-d, but not the control peptides, demonstrated a dose-dependant dominant negative effect on the Tar-1 TM homodimerization in the bacterial ToxR assembly system, suggesting a wild-type-like interaction; and most interestingly, (iii) both Tar-1 all-l and all-d showed a remarkable ability to inhibit the chemotaxis response of the full-length receptor, in vivo. Peptide binding to the bacteria was confirmed through confocal imaging, and Western blotting confirmed that ToxR Tar-1 chimera protein levels are not affected by the presence of the exogenous peptides. These findings present the first evidence that an all-d TM domain peptide acts in vivo similarly to its parental all-l peptide and suggest that the dimerization of the TM domains is mainly mediated by side-chain interactions, rather than geometrically fitted conformations. In addition, the study provides a new approach for modifying the function of membrane proteins by proteolysis-free peptides.
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Affiliation(s)
- Neta Sal-Man
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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41
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Ali MH, Peisach E, Allen KN, Imperiali B. X-ray structure analysis of a designed oligomeric miniprotein reveals a discrete quaternary architecture. Proc Natl Acad Sci U S A 2004; 101:12183-8. [PMID: 15302930 PMCID: PMC514454 DOI: 10.1073/pnas.0401245101] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The x-ray crystal structure of an oligomeric miniprotein has been determined to a 1.2-A resolution by means of multiwavelength anomalous diffraction phasing with selenomethionine analogs that retain the biophysical characteristics of the native peptide. Peptide 1, comprising alpha and beta secondary structure elements with only 21 aa per monomer, associates as a discrete tetramer. The peptide adopts a previously uncharacterized quaternary structure in which alpha and beta components interact to form a tightly packed and well defined hydrophobic core. The structure provides insight into the origins of the unusual thermal stability of the oligomer. The miniprotein shares many characteristics of larger proteins, including cooperative folding, lack of 1-anilino-8-naphthalene sulfonate binding, and limited deuterium exchange, and possesses a buried surface area typical of native proteins.
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Affiliation(s)
- Mayssam H Ali
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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Adams CM, Kjeldsen F, Zubarev RA, Budnik BA, Haselmann KF. Electron capture dissociation distinguishes a single D-amino acid in a protein and probes the tertiary structure. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2004; 15:1087-98. [PMID: 15234367 DOI: 10.1016/j.jasms.2004.04.026] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 04/06/2004] [Accepted: 04/06/2004] [Indexed: 05/11/2023]
Abstract
First results are reported on the application of ECD in analysis of 2+ and 3+ ions of stereoisomers of Trp-cage (NLYIQWLKDGGPSSGRPPPS), the smallest and fastest-folding protein, which exhibits a tightly folded tertiary structure in solution. The chiral recognition based on the ratios of the abundances of z(18) and z(19) fragments in ECD of 2+ ions was excellent even for a single amino acid (Tyr) D-substitution (R(chiral) = 8.6). The chiral effect decreased with an increase of temperature at the electrospray ion source, as well as at a higher degree of ionization, 3+ ions (R(chiral) = 1.5). A general approach is suggested for charge localization in n+ ions by analysis of ECD mass spectra of (n + 1)+ ions. Application of this approach to 3+ Trp-cage ions revealed the protonation probability order in 2+ ions: Arg(16) >> Gln(5) > approximately N-terminus. The ECD results for native form of the 2+ ions favor the preservation of the solution-phase tertiary structure, and chiral recognition through the interaction between the charges and the neutral bond network. Conversely, ECD of 3+ ions supports the dominance of ionic hydrogen bonding which determines a different gas-phase structure than found in solution. Vibrational activation of 2+ ions indicated greater stability of the native form, but the fragmentation patterns did not provide stereoisomer differentiation, thus underlying the special position of ECD among other MS/MS fragmentation techniques. Further ECD studies should yield more structural information as well as quantitative single-amino acid D/L content measurements in proteins.
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Affiliation(s)
- Christopher M Adams
- Laboratory for Biological and Medical Mass Spectrometry, Uppsala University, Uppsala, Sweden
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Glaser RW, Sachse C, Dürr UHN, Wadhwani P, Ulrich AS. Orientation of the antimicrobial peptide PGLa in lipid membranes determined from 19F-NMR dipolar couplings of 4-CF3-phenylglycine labels. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 168:153-63. [PMID: 15082261 DOI: 10.1016/j.jmr.2004.02.008] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Revised: 02/02/2004] [Indexed: 05/03/2023]
Abstract
A highly sensitive solid state (19)F-NMR strategy is described to determine the orientation and dynamics of membrane-associated peptides from specific fluorine labels. Several analogues of the antimicrobial peptide PGLa were synthesized with the non-natural amino acid 4-trifluoromethyl-phenylglycine (CF(3)-Phg) at different positions throughout the alpha-helical peptide chain. A simple 1-pulse (19)F experiment allows the simultaneous measurement of both the anisotropic chemical shift and the homonuclear dipolar coupling within the rotating CF(3)-group in a macroscopically oriented membrane sample. The value and sign of the dipolar splitting determines the tilt of the CF(3)-rotational axis, which is rigidly attached to the peptide backbone, with respect to the external magnetic field direction. Using four CF(3)-labeled peptide analogues (with L-CF(3)-Phg at Ile9, Ala10, Ile13, and Ala14) we confirmed that PGLa is aligned at the surface of lipid membranes with its helix axis perpendicular to the bilayer normal at a peptide:lipid ratio of 1:200. We also determined the azimuthal rotation angle of the helix, which agrees well with the orientation expected from its amphiphilic character. Peptide analogues with a D-CF(3)-Phg label resulting from racemization of the amino acid during synthesis were separately collected by HPLC. Their spectra provide additional information about the PGLa structure and orientation but allow only to discriminate qualitatively between multiple solutions. The structural and functional characterization of the individual CF(3)-labeled peptides by circular dichroism and antimicrobial assays showed only small effects for our four substitutions on the hydrophobic face of the helix, but a significant disturbance was observed in a fifth analogue where Ala8 on the hydrophilic face had been replaced. Even though the hydrophobic CF(3)-Phg side chain cannot be utilized in all positions, it allows highly sensitive NMR measurements over a wide range of experimental conditions and dynamic regimes of the peptide.
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Affiliation(s)
- Ralf W Glaser
- Institute of Biochemistry and Biophysics, Friedrich-Schiller-Universität Jena, Hans-Knöll-Str. 2, 07745 Jena, Germany
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Chelli R, Gervasio FL, Procacci P, Schettino V. Inter-residue and solvent-residue interactions in proteins: a statistical study on experimental structures. Proteins 2004; 55:139-51. [PMID: 14997548 DOI: 10.1002/prot.20030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A large set of protein structures resolved by X-ray or NMR techniques has been extracted from the Protein Data Bank and analyzed using statistical methods. In particular, we investigate the interactions between side chains and the interactions between solvent and side chains, pointing out on the possibility of including the solvent as part of a knowledge-based potential. The solvent-residue contacts are accounted for on the basis of the Voronoi's polyhedron analysis. Our investigation confirms the importance of hydrophobic residues in determining the protein stability. We observe that in general hydrophobic-hydrophobic interactions and, more specifically, aromatic-aromatic contacts tend to be increasingly distally separated in the primary sequence of proteins, thus connecting distinct secondary structure elements. A simple relation expressing the dependence of the protein free energy by the number of residues is proposed. Such a relation includes both the residue-residue and the solvent-residue contributions. The former is dominant for large size proteins, whereas for small sizes (number of residues less than 100) the two terms are comparable. Gapless threading experiments show that the solvent-residue knowledge-based potential yields a significant contribution with respect to discriminating the native structure of proteins. Such contribution is important especially for proteins of small size and is similar to that given by the most favorable residue-residue knowledge-based potential referring to hydrophobic-hydrophobic interactions such as isoleucine-leucine. In general, the inclusion of the solvent-residue interaction produces a relevant increase of the free energy gap between the native structures and decoys.
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Affiliation(s)
- Riccardo Chelli
- Dipartimento di Chimica, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
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Yang H, Zheng G, Peng X, Qiang B, Yuan J. D-Amino acids and D-Tyr-tRNA(Tyr) deacylase: stereospecificity of the translation machine revisited. FEBS Lett 2003; 552:95-8. [PMID: 14527667 DOI: 10.1016/s0014-5793(03)00858-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Until 30 years ago, it had been considered that D-amino acids were excluded from living systems except for D-amino acids in the cell wall of microorganisms. However, D-amino acids, in the form of free amino acids, peptides and proteins, were recently detected in various living organisms from bacteria to mammals. The extensive distribution of bio-functional D-amino acids challenges the current concept of protein synthesis: more attention should be paid to the stereospecificity of the translation machine. Besides aminoacyl-tRNA synthetases, elongation factor Tu and some other mechanisms, D-Tyr-tRNA(Tyr) deacylases provide a novel checkpoint since they specifically recycle misaminoacylated D-Tyr-tRNA(Tyr) and some other D-aminoacyl-tRNAs. Their unique structure represents a new class of tRNA-dependent hydrolase. These unexpected findings have far-reaching implications for our understanding of protein synthesis and its origin.
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Affiliation(s)
- Hongbo Yang
- Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, 5 Dong Dan San Tiao, 100005 Beijing, PR China
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Kleywegt GJ, Henrick K, Dodson EJ, van Aalten DMF. Pound-wise but penny-foolish: How well do micromolecules fare in macromolecular refinement? Structure 2003; 11:1051-9. [PMID: 12962624 DOI: 10.1016/s0969-2126(03)00186-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
For the refinement of protein and nucleic acid structures, high-quality geometric restraint libraries are available. Unfortunately, for other compounds, such as physiological ligands, lead compounds, substrate analogs, etc., the situation is not as favorable. As a result, the structures of small molecules found in complexes with biomacromolecules are often less reliable than those of the surrounding amino or nucleic acids. Here, we briefly review the use of geometric restraints in structure refinement (be it against X-ray crystallographic or NMR-derived data) and simulation. In addition, we discuss methods to generate both restraint libraries and (idealized) coordinates for small molecules and provide some practical advice.
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Affiliation(s)
- Gerard J Kleywegt
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Centre, Box 596, SE-751 24 Uppsala, Sweden.
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