1
|
Best W, Ferrell M, Boris A, Heydarian N, Panlilio H, Rice CV. Acquisition of Resistance to PEGylated Branched Polyethylenimine Increases Pseudomonas Aeruginosa Susceptibility to Aminoglycosides. ChemMedChem 2024; 19:e202300689. [PMID: 38806411 PMCID: PMC11368615 DOI: 10.1002/cmdc.202300689] [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: 12/06/2023] [Revised: 05/24/2024] [Accepted: 05/24/2024] [Indexed: 05/30/2024]
Abstract
PEGylated branched polyethylenimine (PEG-BPEI) has antibacterial and antibiofilm properties. Exposure to PEG-BPEI through serial passage leads to resistant P. aeruginosa strains. The minimum inhibitory concentration (MIC) of 600 Da BPEI and PEGylated 600 Da BPEI (PEG-BPEI) in the wild-type PAO1 strain is 16 μg/ml while, after 15 serial passages, the MIC increased to 1024 μg/mL. An additional 15 rounds of serial passage in the absence of BPEI or PEG-BPEI did not change the 1024 μg/mL MIC. Gentamicin, Neomycin, and Tobramycin, cationic antibiotics that inhibit protein synthesis, have a 16-32 fold reduction of MIC values in PEG350-BPEI resistant strains, suggesting increased permeation. The influx of these antibiotics occurs using a self-mediated uptake mechanism, suggesting changes to the outer membrane Data show that resistance causes changes in genes related to outer membrane lipopolysaccharide (LPS) assembly. Mutations were noted in the gene coding for the polymerase Wzy that participates in the assembly of the O-antigen region. Other mutations were noted with wbpE and wbpI of the Wbp pathway responsible for the enzymatic synthesis of ManNAc(3NAc)A in the LPS of P. aeruginosa. These changes suggest that an altered gene product could lead to PEG-BPEI resistance. Nevertheless, the increased susceptibility to aminoglycosides could prevent the emergence of PEG-BPEI resistant bacterial populations.
Collapse
Affiliation(s)
- William Best
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| | - Maya Ferrell
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| | - Andrew Boris
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| | - Neda Heydarian
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| | - Hannah Panlilio
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| | - Charles V. Rice
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73069
| |
Collapse
|
2
|
Tamucci JD, Alder NN, May ER. Peptide Power: Mechanistic Insights into the Effect of Mitochondria-Targeted Tetrapeptides on Membrane Electrostatics from Molecular Simulations. Mol Pharm 2023; 20:6114-6129. [PMID: 37904323 PMCID: PMC10841697 DOI: 10.1021/acs.molpharmaceut.3c00480] [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] [Indexed: 11/01/2023]
Abstract
Mitochondrial dysfunction is implicated in nine of the ten leading causes of death in the US, yet there are no FDA-approved therapeutics to treat it. Synthetic mitochondria-targeted peptides (MTPs), including the lead compound SS-31, offer promise, as they have been shown to restore healthy mitochondrial function and treat a variety of common diseases. At the cellular level, research has shown that MTPs accumulate strongly at the inner mitochondrial membrane (IMM), slow energy sinks (e.g., proton leaks), and improve ATP production. Modulation of electrostatic fields around the IMM has been implicated as a key aspect in the mechanism of action (MoA) of these peptides; however, molecular and mechanistic details have remained elusive. In this study, we employed all-atom molecular dynamics simulations (MD) to investigate the interactions of four MTPs with lipid bilayers and calculate their effect on structural and electrostatic properties. In agreement with previous experimental findings, we observed the modulation of the membrane surface and dipole potentials by MTPs. The simulations reveal that the MTPs achieve a reduction in the dipole potential by acting to disorder both lipid head groups and water layers proximal to the bilayer surface. We also find that MTPs decrease the bilayer thickness and increase the membrane's capacitance. These changes suggest that MTPs may enhance how much potential energy can be stored across the IMM at a given transmembrane potential difference. The MTPs also displace cations away from the bilayer surface, modulating the surface potential and offering an alternative mechanism for how these MTPs reduce mitochondrial energy sinks like proton leaks and mitigate Ca2+ accumulation stress. In conclusion, this study highlights the therapeutic potential of MTPs and underlines how interactions of MTPs with lipid bilayers serve as a fundamental component of their MoA.
Collapse
Affiliation(s)
- Jeffrey D Tamucci
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Eric R May
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, United States
| |
Collapse
|
3
|
Sun S, Karki C, Aguilera J, Hernandez AEL, Sun J, Li L. Computational Study on the Function of Palmitoylation on the Envelope Protein in SARS-CoV-2. J Chem Theory Comput 2021; 17:6483-6490. [PMID: 34516136 PMCID: PMC8457325 DOI: 10.1021/acs.jctc.1c00359] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Indexed: 01/02/2023]
Abstract
SARS-CoV-2 that caused COVID-19 has spread since the end of 2019. Its major effects resulted in over four million deaths around the whole world by August 2021. Therefore, understanding virulence mechanisms is important to prevent future outbreaks and for COVID-19 drug development. The envelope (E) protein is an important structural protein, affecting virus assembly and budding. The E protein pentamer is a viroporin, serving as an ion transferring channel in cells. In this work, we applied molecular dynamic simulations and topological and electrostatic analyses to study the effects of palmitoylation on the E protein pentamer. The results indicate that the cation transferring direction is more from the lumen to the cytosol. The structure of the palmitoylated E protein pentamer is more stable while the loss of palmitoylation caused the pore radius to reduce and even collapse. The electrostatic forces on the two sides of the palmitoylated E protein pentamer are more beneficial to attract cations in the lumen and to release cations into the cytosol. The results indicate the importance of palmitoylation, which can help the drug design for the treatment of COVID-19.
Collapse
Affiliation(s)
- Shengjie Sun
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| | - Chitra Karki
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| | - Javier Aguilera
- Department of Biological Sciences and Border Biomedical Research Center, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| | - Alan E Lopez Hernandez
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| | - Jianjun Sun
- Department of Biological Sciences and Border Biomedical Research Center, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| | - Lin Li
- Computational Science Program, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
- Department of Physics, The University of Texas at El Paso, 500 W University Ave, TX, 79968, USA
| |
Collapse
|
4
|
Cetuk H, Anishkin A, Scott AJ, Rempe SB, Ernst RK, Sukharev S. Partitioning of Seven Different Classes of Antibiotics into LPS Monolayers Supports Three Different Permeation Mechanisms through the Outer Bacterial Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:1372-1385. [PMID: 33449700 DOI: 10.1021/acs.langmuir.0c02652] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The outer membrane (OM) of Gram-negative (G-) bacteria presents a barrier for many classes of antibacterial agents. Lipopolysaccharide (LPS), present in the outer leaflet of the OM, is stabilized by divalent cations and is considered to be the major impediment for antibacterial agent permeation. However, the actual affinities of major antibiotic classes toward LPS have not yet been determined. In the present work, we use Langmuir monolayers formed from E. coli Re and Rd types of LPS to record pressure-area isotherms in the presence of antimicrobial agents. Our observations suggest three general types of interactions. First, some antimicrobials demonstrated no measurable interactions with LPS. This lack of interaction in the case of cefsulodin, a third-generation cephalosporin antibiotic, correlates with its low efficacy against G- bacteria. Ampicillin and ciprofloxacin also show no interactions with LPS, but in contrast to cefsulodin, both exhibit good efficacy against G- bacteria, indicating permeation through common porins. Second, we observe substantial intercalation of the more hydrophobic antibiotics, novobiocin, rifampicin, azithromycin, and telithromycin, into relaxed LPS monolayers. These largely repartition back to the subphase with monolayer compression. We find that the hydrophobic area, charge, and dipole all show correlations with both the mole fraction of antibiotic retained in the monolayer at the monolayer-bilayer equivalence pressure and the efficacies of these antibiotics against G- bacteria. Third, amine-rich gentamicin and the cationic antimicrobial peptides polymyxin B and colistin show no hydrophobic insertion but are instead strongly driven into the polar LPS layer by electrostatic interactions in a pressure-independent manner. Their intercalation stably increases the area per molecule (by up to 20%), which indicates massive formation of defects in the LPS layer. These defects support a self-promoted permeation mechanism of these antibiotics through the OM, which explains the high efficacy and specificity of these antimicrobials against G- bacteria.
Collapse
Affiliation(s)
- Hannah Cetuk
- Biology Department, University of Maryland, College Park, Maryland 20742, United States
| | - Andriy Anishkin
- Biology Department, University of Maryland, College Park, Maryland 20742, United States
| | - Alison J Scott
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore Maryland 21201, United States
| | - Susan B Rempe
- Center for Chemical, Biological, Radiation, and Nuclear Defense and Energy Technology, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore Maryland 21201, United States
| | - Sergei Sukharev
- Biology Department, University of Maryland, College Park, Maryland 20742, United States
| |
Collapse
|
5
|
Lam AK, Moen EL, Pusavat J, Wouters CL, Panlilio H, Ferrell MJ, Houck MB, Glatzhofer DT, Rice CV. PEGylation of Polyethylenimine Lowers Acute Toxicity while Retaining Anti-Biofilm and β-Lactam Potentiation Properties against Antibiotic-Resistant Pathogens. ACS OMEGA 2020; 5:26262-26270. [PMID: 33073153 PMCID: PMC7557992 DOI: 10.1021/acsomega.0c04111] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 09/15/2020] [Indexed: 05/29/2023]
Abstract
Bacterial biofilms, often impenetrable to antibiotic medications, are a leading cause of poor wound healing. The prognosis is worse for wounds with biofilms of antimicrobial-resistant (AMR) bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and multi-drug resistant Pseudomonas aeruginosa (MDR-PA). Resistance hinders initial treatment of standard-of-care antibiotics. The persistence of MRSA, MRSE, and/or MDR-PA often allows acute infections to become chronic wound infections. The water-soluble hydrophilic properties of low-molecular-weight (600 Da) branched polyethylenimine (600 Da BPEI) enable easy drug delivery to directly attack AMR and biofilms in the wound environment as a topical agent for wound treatment. To mitigate toxicity issues, we have modified 600 Da BPEI with polyethylene glycol (PEG) in a straightforward one-step reaction. The PEG-BPEI molecules disable β-lactam resistance in MRSA, MRSE, and MDR-PA while also having the ability to dissolve established biofilms. PEG-BPEI accomplishes these tasks independently, resulting in a multifunction potentiation agent. We envision wound treatment with antibiotics given topically, orally, or intravenously in which external application of PEG-BPEIs disables biofilms and resistance mechanisms. In the absence of a robust pipeline of new drugs, existing drugs and regimens must be re-evaluated as combination(s) with potentiators. The PEGylation of 600 Da BPEI provides new opportunities to meet this goal with a single compound whose multifunction properties are retained while lowering acute toxicity.
Collapse
|
6
|
Dezanet C, Kempf J, Mingeot-Leclercq MP, Décout JL. Amphiphilic Aminoglycosides as Medicinal Agents. Int J Mol Sci 2020; 21:E7411. [PMID: 33049963 PMCID: PMC7583001 DOI: 10.3390/ijms21197411] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 09/27/2020] [Accepted: 10/02/2020] [Indexed: 12/25/2022] Open
Abstract
The conjugation of hydrophobic group(s) to the polycationic hydrophilic core of the antibiotic drugs aminoglycosides (AGs), targeting ribosomal RNA, has led to the development of amphiphilic aminoglycosides (AAGs). These drugs exhibit numerous biological effects, including good antibacterial effects against susceptible and multidrug-resistant bacteria due to the targeting of bacterial membranes. In the first part of this review, we summarize our work in identifying and developing broad-spectrum antibacterial AAGs that constitute a new class of antibiotic agents acting on bacterial membranes. The target-shift strongly improves antibiotic activity against bacterial strains that are resistant to the parent AG drugs and to antibiotic drugs of other classes, and renders the emergence of resistant Pseudomonas aeruginosa strains highly difficult. Structure-activity and structure-eukaryotic cytotoxicity relationships, specificity and barriers that need to be crossed in their development as antibacterial agents are delineated, with a focus on their targets in membranes, lipopolysaccharides (LPS) and cardiolipin (CL), and the corresponding mode of action against Gram-negative bacteria. At the end of the first part, we summarize the other recent advances in the field of antibacterial AAGs, mainly published since 2016, with an emphasis on the emerging AAGs which are made of an AG core conjugated to an adjuvant or an antibiotic drug of another class (antibiotic hybrids). In the second part, we briefly illustrate other biological and biochemical effects of AAGs, i.e., their antifungal activity, their use as delivery vehicles of nucleic acids, of short peptide (polyamide) nucleic acids (PNAs) and of drugs, as well as their ability to cleave DNA at abasic sites and to inhibit the functioning of connexin hemichannels. Finally, we discuss some aspects of structure-activity relationships in order to explain and improve the target selectivity of AAGs.
Collapse
Affiliation(s)
- Clément Dezanet
- Molecular Pharmacochemistry Department, University Grenoble Alpes, CNRS, 470 Rue de la Chimie, F-38000 Grenoble, France; (C.D.); (J.K.)
| | - Julie Kempf
- Molecular Pharmacochemistry Department, University Grenoble Alpes, CNRS, 470 Rue de la Chimie, F-38000 Grenoble, France; (C.D.); (J.K.)
| | - Marie-Paule Mingeot-Leclercq
- Cellular and Molecular Pharmacology Unit, Louvain Drug Research Institute, Catholic University of Louvain, Avenue E. Mounier 73, UCL B1.73.05, 1200 Brussels, Belgium
| | - Jean-Luc Décout
- Molecular Pharmacochemistry Department, University Grenoble Alpes, CNRS, 470 Rue de la Chimie, F-38000 Grenoble, France; (C.D.); (J.K.)
| |
Collapse
|
7
|
Lam AK, Panlilio H, Pusavat J, Wouters CL, Moen EL, Rice CV. Overcoming Multidrug Resistance and Biofilms of Pseudomonas aeruginosa with a Single Dual-Function Potentiator of β-Lactams. ACS Infect Dis 2020; 6:1085-1097. [PMID: 32223216 PMCID: PMC7233300 DOI: 10.1021/acsinfecdis.9b00486] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Clinicians prescribe hundreds of millions of β-lactam antibiotics to treat the majority of patients presenting with bacterial infections. Patient outcomes are positive unless resistant bacteria, such as Pseudomonas aeruginosa (P. aeruginosa), are present. P. aeruginosa has both intrinsic and acquired antibiotic resistance, making clinical management of infection a real challenge, particularly when these bacteria are sequestered in biofilms. These problems would be alleviated if, upon the initial presentation of bacterial infection symptoms, clinicians were able to administer an antibiotic that kills both susceptible and otherwise resistant bacteria and eradicates biofilms. As the most common class of antibiotics, β-lactams could be used in a new drug if the leading causes of β-lactam antibiotic resistance, permeation barriers from lipopolysaccharide, efflux pumps, and β-lactamase enzymes, were also defeated. Against P. aeruginosa and their biofilms, the potency of β-lactam antibiotics is restored with 600 Da branched polyethylenimine (600 Da BPEI). Checkerboard assays using microtiter plates demonstrate the potentiation of piperacillin, cefepime, Meropenem, and erythromycin antibiotics. Growth curves demonstrate that only a combination of 600 Da BPEI and piperacillin produces growth inhibition against antibiotic resistant P. aeruginosa. Scanning electron microscopy (SEM) was used to confirm that the combination treatment leads to abnormal P. aeruginosa morphology. Data collected with isothermal titration calorimetry and fluorescence spectroscopy demonstrate a mechanism of action in which potentiation at low concentrations of 600 Da BPEI reduces diffusion barriers from lipopolysaccharides without disrupting the outer membrane itself. Coupled with the ability to overcome a reduction in antibiotic activity created by biofilm exopolymers, targeting anionic sites on lipopolysaccharides and biofilm exopolysaccharides with the same compound provides new opportunities to counter the rise of multidrug-resistant infections.
Collapse
Affiliation(s)
- Anh K Lam
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Hannah Panlilio
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Jennifer Pusavat
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Cassandra L Wouters
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Erika L Moen
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Charles V Rice
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| |
Collapse
|
8
|
Karki C, Xian Y, Xie Y, Sun S, Lopez-Hernandez AE, Juarez B, Wang J, Sun J, Li L. A computational model of ESAT-6 complex in membrane. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2020; 19:2040002. [PMID: 34211240 PMCID: PMC8245204 DOI: 10.1142/s0219633620400027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
One quarter of the world's population are infected by Mycobacterium tuberculosis (Mtb), which is a leading death-causing bacterial pathogen. Recent evidence has demonstrated that two virulence factors, ESAT-6 and CFP-10, play crucial roles in Mtb's cytosolic translocation. Many efforts have been made to study the ESAT-6 and CFP-10 proteins. Some studies have shown that ESAT-6 has an essential role in rupturing phagosome. However, the mechanisms of how ESAT-6 interacts with the membrane have not yet been fully understood. Recent studies indicate that the ESAT-6 disassociates with CFP-10 upon their interaction with phagosome membrane, forming a membrane-spanning pore. Based on these observations, as well as the available structure of ESAT-6, ESAT-6 is hypothesized to form an oligomer for membrane insertion as well as rupturing. Such an ESAT-6 oligomer may play a significant role in the tuberculosis infection. Therefore, deeper understanding of the oligomerization of ESAT-6 will establish new directions for tuberculosis treatment. However, the structure of the oligomer of ESAT-6 is not known. Here, we proposed a comprehensive approach to model the complex structures of ESAT-6 oligomer inside a membrane. Several computational tools, including MD simulation, symmetrical docking, MM/PBSA, are used to obtain and characterize such a complex structure. Results from our studies lead to a well-supported hypothesis of the ESAT-6 oligomerization as well as the identification of essential residues in stabilizing the ESAT-6 oligomer which provide useful insights for future drug design targeting tuberculosis. The approach in this research can also be used to model and study other cross-membrane complex structures.
Collapse
Affiliation(s)
- Chitra Karki
- Department of Physics, University of Texas at El Paso, El Paso, Texas
- Computational Science Program, University of Texas at El Paso, El Paso, Texas
| | - Yuejiao Xian
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas
| | - Yixin Xie
- Computational Science Program, University of Texas at El Paso, El Paso, Texas
| | - Shengjie Sun
- Computational Science Program, University of Texas at El Paso, El Paso, Texas
| | | | - Brenda Juarez
- Department of Physics, University of Texas at El Paso, El Paso, Texas
| | - Jun Wang
- Department of Physics, University of Texas at El Paso, El Paso, Texas
| | - Jianjun Sun
- Department of Biology, University of Texas at El Paso, El Paso, Texas
| | - Lin Li
- Department of Physics, University of Texas at El Paso, El Paso, Texas
| |
Collapse
|
9
|
Gnandt D, Koslowski T. Long-range electron-electron interaction and charge transfer in protein complexes: a numerical approach. Phys Chem Chem Phys 2019; 21:18595-18604. [PMID: 31414082 DOI: 10.1039/c9cp03141c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
With application to the nitrite reductase hexameric protein complex of Desulfovibrio vulgaris, NrfH2A4, we suggest a strategy to compute the energy landscape of electron transfer in large systems of biochemical interest. For small complexes, the energy of all electronic configurations can be scanned completely on the level of a numerical solution of the Poisson-Boltzmann equation. In contrast, larger systems have to be treated using a pair approximation, which is verified here. Effective Coulomb interactions between neighbouring sites of excess electron localization may become as large as 200 meV, and they depend in a nontrivial manner on the intersite distance. We discuss the implications of strong Coulomb interactions on the thermodynamics and kinetics of charging and decharging a protein complex. Finally, we turn to the effect of embedding the system into a biomembrane.
Collapse
Affiliation(s)
- David Gnandt
- Institut für Physikalische Chemie, Universität Freiburg, Albertstraße 23a, 79104 Freiburg im Breisgau, Germany.
| | | |
Collapse
|
10
|
Li A, Schertzer JW, Yong X. Molecular dynamics modeling of Pseudomonas aeruginosa outer membranes. Phys Chem Chem Phys 2018; 20:23635-23648. [PMID: 30191217 DOI: 10.1039/c8cp04278k] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Pseudomonas aeruginosa is a common Gram-negative bacterium and opportunistic human pathogen. The distinctive structure of its outer membrane (OM) and outer membrane vesicles (OMVs) plays a fundamental role in bacterial virulence, colonization ability, and antibiotic resistance. To provide critical insights into OM and OMV functionality, we conducted an all-atom molecular dynamics study of asymmetric membranes that are biologically relevant to P. aeruginosa. We hybridized a GLYCAM06-based lipopolysaccharides force field with the Stockholm lipids force field (Slipids) to model bilayer membranes with Lipid A molecules in one leaflet and physiologically relevant phospholipid molecules in the other, including 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), and 1,2-dioleoyl-sn-glycero-3-phosphoglycerol (DOPG). In particular, a membrane with phospholipid composition representing the P. aeruginosa OM was constructed and modeled by mixing the physiologically dominant components. The detailed structure of membranes was characterized by area per lipid, transmembrane mass and charge densities, radial distribution function (RDF), deuterium order parameter (SCD) of acyl chains, and inclination angles of phosphates and disaccharide in Lipid A. The membrane fluidity in equilibrium and the hydration of functional groups were probed and characterized quantitatively. The consistent properties of the Lipid A leaflets in different membranes demonstrate its compatibility with various phospholipids present in the P. aeruginosa OM. The more ordered acyl chains of Lipid A compared to the cytoplasmic cell membrane contribute to the low permeability of bacterial outer membrane. The findings of this computational investigation of P. aeruginosa OM will further the understanding of microbial pathogenesis and enable future study of OMV biogenesis.
Collapse
Affiliation(s)
- Ao Li
- Department of Mechanical Engineering, Binghamton University, The State University of New York, Binghamton, New York 13902, USA.
| | | | | |
Collapse
|
11
|
Li L, Chakravorty A, Alexov E. DelPhiForce, a tool for electrostatic force calculations: Applications to macromolecular binding. J Comput Chem 2017; 38:584-593. [PMID: 28130775 PMCID: PMC5315605 DOI: 10.1002/jcc.24715] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/10/2016] [Indexed: 12/31/2022]
Abstract
Long-range electrostatic forces play an important role in molecular biology, particularly in macromolecular interactions. However, calculating the electrostatic forces for irregularly shaped molecules immersed in water is a difficult task. Here, we report a new tool, DelPhiForce, which is a tool in the DelPhi package that calculates and visualizes the electrostatic forces in biomolecular systems. In parallel, the DelPhi algorithm for modeling electrostatic potential at user-defined positions has been enhanced to include triquadratic and tricubic interpolation methods. The tricubic interpolation method has been tested against analytical solutions and it has been demonstrated that the corresponding errors are negligibly small at resolution 4 grids/Å. The DelPhiForce is further applied in the study of forces acting between partners of three protein-protein complexes. It has been demonstrated that electrostatic forces play a dual role by steering binding partners (so that the partners recognize their native interfaces) and exerting an electrostatic torque (if the mutual orientations of the partners are not native-like). The output of DelPhiForce is in a format that VMD can read and visualize, and provides additional options for analysis of protein-protein binding. DelPhiForce is available for download from the DelPhi webpage at http://compbio.clemson.edu/downloadDir/delphiforce.tar.gz © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Lin Li
- Department of Physics, Clemson University, Clemson, SC 29634, USA
| | | | - Emil Alexov
- Department of Physics, Clemson University, Clemson, SC 29634, USA
| |
Collapse
|
12
|
Greene D, Botello-Smith WM, Follmer A, Xiao L, Lambros E, Luo R. Modeling Membrane Protein-Ligand Binding Interactions: The Human Purinergic Platelet Receptor. J Phys Chem B 2016; 120:12293-12304. [PMID: 27934233 PMCID: PMC5460638 DOI: 10.1021/acs.jpcb.6b09535] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Membrane proteins, due to their roles as cell receptors and signaling mediators, make prime candidates for drug targets. The computational analysis of protein-ligand binding affinities has been widely employed as a tool in rational drug design efforts. Although efficient implicit solvent-based methods for modeling globular protein-ligand binding have been around for many years, the extension of such methods to membrane protein-ligand binding is still in its infancy. In this study, we extended the widely used Amber/MMPBSA method to model membrane protein-ligand systems, and we used it to analyze protein-ligand binding for the human purinergic platelet receptor (P2Y12R), a prominent drug target in the inhibition of platelet aggregation for the prevention of myocardial infarction and stroke. The binding affinities, computed by the Amber/MMPBSA method using standard parameters, correlate well with experiment. A detailed investigation of these parameters was conducted to assess their impact on the accuracy of the method. These analyses show the importance of properly treating the nonpolar solvation interactions and the electrostatic polarization in the binding of nucleotide agonists and non-nucleotide antagonists to P2Y12R. On the basis of the crystal structures and the experimental conditions in the binding assay, we further hypothesized that the nucleotide agonists lose their bound magnesium ion upon binding to P2Y12R, and our computational study supports this hypothesis. Ultimately, this work illustrates the value of computational analysis in the interpretation of experimental binding reactions.
Collapse
Affiliation(s)
- D'Artagnan Greene
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Wesley M. Botello-Smith
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Chemical and Materials Physics Graduate Program, University of California, Irvine, CA 92697
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Alec Follmer
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Li Xiao
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Department of Biomedical Engineering, University of California, Irvine, CA 92697
| | - Eleftherios Lambros
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Ray Luo
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
- Chemical and Materials Physics Graduate Program, University of California, Irvine, CA 92697
- Department of Biomedical Engineering, University of California, Irvine, CA 92697
- Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697
| |
Collapse
|
13
|
Li L, Alper J, Alexov E. Cytoplasmic dynein binding, run length, and velocity are guided by long-range electrostatic interactions. Sci Rep 2016; 6:31523. [PMID: 27531742 PMCID: PMC4987762 DOI: 10.1038/srep31523] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 07/21/2016] [Indexed: 12/23/2022] Open
Abstract
Dyneins are important molecular motors involved in many essential biological processes, including cargo transport along microtubules, mitosis, and in cilia. Dynein motility involves the coupling of microtubule binding and unbinding to a change in the configuration of the linker domain induced by ATP hydrolysis, which occur some 25 nm apart. This leaves the accuracy of dynein stepping relatively inaccurate and susceptible to thermal noise. Using multi-scale modeling with a computational focusing technique, we demonstrate that the microtubule forms an electrostatic funnel that guides the dynein's microtubule binding domain (MTBD) as it finally docks to the precise, keyed binding location on the microtubule. Furthermore, we demonstrate that electrostatic component of the MTBD's binding free energy is linearly correlated with the velocity and run length of dynein, and we use this linearity to predict the effect of mutating each glutamic and aspartic acid located in MTBD domain to alanine. Lastly, we show that the binding of dynein to the microtubule is associated with conformational changes involving several helices, and we localize flexible hinge points within the stalk helices. Taken all together, we demonstrate that long range electrostatic interactions bring a level of precision to an otherwise noisy dynein stepping process.
Collapse
Affiliation(s)
- Lin Li
- Department of Physics, Clemson University, Clemson, SC 29634, USA
| | - Joshua Alper
- Department of Physics, Clemson University, Clemson, SC 29634, USA
| | - Emil Alexov
- Department of Physics, Clemson University, Clemson, SC 29634, USA
| |
Collapse
|
14
|
Santos HAF, Vila-Viçosa D, Teixeira VH, Baptista AM, Machuqueiro M. Constant-pH MD Simulations of DMPA/DMPC Lipid Bilayers. J Chem Theory Comput 2015; 11:5973-9. [DOI: 10.1021/acs.jctc.5b00956] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | - António M. Baptista
- Instituto
de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | | |
Collapse
|
15
|
Zgurskaya HI, López CA, Gnanakaran S. Permeability Barrier of Gram-Negative Cell Envelopes and Approaches To Bypass It. ACS Infect Dis 2015; 1:512-522. [PMID: 26925460 DOI: 10.1021/acsinfecdis.5b00097] [Citation(s) in RCA: 377] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gram-negative bacteria are intrinsically resistant to many antibiotics. Species that have acquired multidrug resistance and cause infections that are effectively untreatable present a serious threat to public health. The problem is broadly recognized and tackled at both the fundamental and applied levels. This paper summarizes current advances in understanding the molecular bases of the low permeability barrier of Gram-negative pathogens, which is the major obstacle in discovery and development of antibiotics effective against such pathogens. Gaps in knowledge and specific strategies to break this barrier and to achieve potent activities against difficult Gram-negative bacteria are also discussed.
Collapse
Affiliation(s)
- Helen I. Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Cesar A. López
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - S. Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| |
Collapse
|
16
|
Ma H, Irudayanathan FJ, Jiang W, Nangia S. Simulating Gram-Negative Bacterial Outer Membrane: A Coarse Grain Model. J Phys Chem B 2015; 119:14668-82. [DOI: 10.1021/acs.jpcb.5b07122] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Huilin Ma
- Department of Biomedical
and Chemical Engineering, Syracuse University, Syracuse, New York 13244, United States
| | | | - Wenjuan Jiang
- Department of Biomedical
and Chemical Engineering, Syracuse University, Syracuse, New York 13244, United States
| | - Shikha Nangia
- Department of Biomedical
and Chemical Engineering, Syracuse University, Syracuse, New York 13244, United States
| |
Collapse
|
17
|
Vila-Viçosa D, Teixeira VH, Santos HAF, Baptista AM, Machuqueiro M. Treatment of Ionic Strength in Biomolecular Simulations of Charged Lipid Bilayers. J Chem Theory Comput 2014; 10:5483-92. [DOI: 10.1021/ct500680q] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Diogo Vila-Viçosa
- Centro
de Química e Bioquímica and Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Vitor H. Teixeira
- Centro
de Química e Bioquímica and Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Hugo A. F. Santos
- Faculty
of Sciences, BioFIG−Centre for Biodiversity, Functional and
Integrative Genomics, University of Lisboa, 1649-004 Lisboa, Portugal
| | - António M. Baptista
- Instituto
de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Miguel Machuqueiro
- Centro
de Química e Bioquímica and Departamento de Química
e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| |
Collapse
|