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Open Access Publications from the University of California

Scholarly Works (14 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2022)

Computers have held an increasingly important place in chemical and biological research. Non-specialists may presume that computers can perform a small number of specialized techniques, but in reality they may be used on a wide range of biological scales to answer disparate questions in biology and chemistry. This body of work exemplifies that, using scales ranging from coarse grained nodes representing amino acids at the cell scale down to electron density clouds. Specifically, the projects here use elastic network models to investigate basic bacterial biology, Brownian dynamics and molecular dynamics to investigate influenza, and quantum mechanics to investigate tuberculosis. In this work we find that the protein sheets of chimallin in Pseudomonas chlororaphis cells infected with jumbo phage 201phi2-1 display a significant amount of flexibility and have several pores which could transport ions or nucleotides. On a different project we found that glycans can inhibit drug binding to influenza, and that the glycoproteins in influenza can access protein conformations amenable to cellular exocytosis and endocytosis. We also find that the flexibility of these glycoproteins opens new epitopes and drug binding sites that cannot be found from their crystal structures. Finally, we develop force field parameters for cytochrome bd-type quinol oxidase, which is a promising drug target for Mycobacterium tuberculosis and Escherichia coli.

    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2023)
    All protein simulations are conducted with varying degrees of simplification, oftentimes with unknown ramifications about how these simplifications affect the interpretability of the results. In this work, we investigated how protein glycosylation and lateral crowding effects modulate an array of properties characterizing the stability and dynamics of influenza neuraminidase. We constructed three systems: (1) glycosylated neuraminidase in a whole virion (i.e., crowded membrane) environment, (2) glycosylated neuraminidase in its own lipid bilayer, and (3) unglycosylated neuraminidase in its own lipid bilayer. We saw that glycans tend to stabilize the protein structure and reduce its conformational flexibility while restricting the solvent movement. Conversely, a crowded membrane environment encouraged exploration of the free energy landscape and a large-scale conformational change, while making the protein structure more compact. Understanding these effects informs what factors one must consider in attempting to recapture the desired level of physical accuracy.
      Cover page: Glycosylation and Crowded Membrane Effects on Influenza Neuraminidase Stability and Dynamics.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2022)
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2021)
        Cytochrome bd -type quinol oxidase is an important metalloenzyme that allows many bacteria to survive in low oxygen conditions. Since bd oxidase is found in many prokaryotes but not in eukaryotes, it has emerged as a promising bacterial drug target. Examples of organisms containing bd oxidases include the Mycobacterium tuberculosis (Mtb) bacterium that causes tuberculosis (TB) in humans, the Vibrio cholerae bacterium that causes cholera, the Pseudomonas aeruginosa bacterium that contributes to antibiotic resistance and sepsis, and the Campylobacter jejuni bacterium that causes food poisoning. Escherichia coli (E. coli) is another organism exhibiting the cytochrome bd oxidase. Since it has the highest sequence identity to Mtb (36 %) and we are ultimately interested in finding drug targets for TB, we have built parameters for the E. coli bd oxidase (Protein Data Bank ID number: 6RKO) that are compatible with the all-atom Amber ff14SB force field for molecular dynamics (MD) simulations. Specifically, we built parameters for the three heme cofactors present in all species of bacterial cytochrome bd -type oxidases (heme b 558 , heme b 595 , and heme d) along with their axial ligands. This data report includes the parameter files that can be used with Amber's LEaP program to generate input files for MD simulations using the Amber software package. We also provide the PDB data files of the initial model both by itself and solvated with TIP3P water molecules and counterions.
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2021)
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2020)
            Influenza neuraminidase is an important drug target. Glycans are present on neuraminidase and are generally considered to inhibit antibody binding via their glycan shield. In this work, we studied the effect of glycans on the binding kinetics of antiviral drugs to the influenza neuraminidase. We created all-atom in silico systems of influenza neuraminidase with experimentally derived glycoprofiles consisting of four systems with different glycan conformations and one system without glycans. Using Brownian dynamics simulations, we observe a two- to eightfold decrease in the rate of ligand binding to the primary binding site of neuraminidase due to the presence of glycans. These glycans are capable of covering much of the surface area of neuraminidase, and the ligand binding inhibition is derived from glycans sterically occluding the primary binding site on a neighboring monomer. Our work also indicates that drugs preferentially bind to the primary binding site (i.e., the active site) over the secondary binding site, and we propose a binding mechanism illustrating this. These results help illuminate the complex interplay between glycans and ligand binding on the influenza membrane protein neuraminidase.
              Cover page: Multiscale Simulations Examining Glycan Shield Effects on Drug Binding to Influenza Neuraminidase
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2021)

              Cytochrome bd-type quinol oxidase is an important metalloenzyme that allows many bacteria to survive in low oxygen conditions. Since bd oxidase is found in many prokaryotes but not in eukaryotes, it has emerged as a promising bacterial drug target. Examples of organisms containing bd oxidases include the Mycobacterium tuberculosis (Mtb) bacterium that causes tuberculosis (TB) in humans, the Vibrio cholerae bacterium that causes cholera, the Pseudomonas aeruginosa bacterium that contributes to antibiotic resistance and sepsis, and the Campylobacter jejuni bacterium that causes food poisoning. Escherichia coli (E. coli) is another organism exhibiting the cytochrome bd oxidase. Since it has the highest sequence identity to Mtb (36 %) and we are ultimately interested in finding drug targets for TB, we have built parameters for the E. coli bd oxidase (Protein Data Bank ID number: 6RKO) that are compatible with the all-atom Amber ff14SB force field for molecular dynamics (MD) simulations. Specifically, we built parameters for the three heme cofactors present in all species of bacterial cytochrome bd-type oxidases (heme b558, heme b595, and heme d) along with their axial ligands. This data report includes the parameter files that can be used with Amber's LEaP program to generate input files for MD simulations using the Amber software package. We also provide the PDB data files of the initial model both by itself and solvated with TIP3P water molecules and counterions.

                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2021)
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2022)
                  Influenza virus has resurfaced recently from inactivity during the early stages of the COVID-19 pandemic, raising serious concerns about the nature and magnitude of future epidemics. The main antigenic targets of influenza virus are two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). Whereas the structural and dynamical properties of both glycoproteins have been studied previously, the understanding of their plasticity in the whole-virion context is fragmented. Here, we investigate the dynamics of influenza glycoproteins in a crowded protein environment through mesoscale all-atom molecular dynamics simulations of two evolutionary-linked glycosylated influenza A whole-virion models. Our simulations reveal and kinetically characterize three main molecular motions of influenza glycoproteins: NA head tilting, HA ectodomain tilting, and HA head breathing. The flexibility of HA and NA highlights antigenically relevant conformational states, as well as facilitates the characterization of a novel monoclonal antibody, derived from convalescent human donor, that binds to the underside of the NA head. Our work provides previously unappreciated views on the dynamics of HA and NA, advancing the understanding of their interplay and suggesting possible strategies for the design of future vaccines and antivirals against influenza.
                    Cover page: Breathing and Tilting: Mesoscale Simulations Illuminate Influenza Glycoprotein Vulnerabilities.
                    • Article
                    • Peer Reviewed
                    UC San Diego Previously Published Works (2021)
                    Cytochrome bd-type quinol oxidase is an important metalloenzyme that allows many bacteria to survive in low oxygen conditions. Since bd oxidase is found in many prokaryotes but not in eukaryotes, it has emerged as a promising bacterial drug target. Examples of organisms containing bd oxidases include the Mycobacterium tuberculosis (Mtb) bacterium that causes tuberculosis (TB) in humans, the Vibrio cholerae bacterium that causes cholera, the Pseudomonas aeruginosa bacterium that contributes to antibiotic resistance and sepsis, and the Campylobacter jejuni bacterium that causes food poisoning. Escherichia coli (E. coli) is another organism exhibiting the cytochrome bd oxidase. Since it has the highest sequence identity to Mtb (36%) and we are ultimately interested in finding drug targets for TB, we have built parameters for the E. coli bd oxidase (Protein Data Bank ID number: 6RKO) that are compatible with the all-atom Amber ff14SB force field for molecular dynamics (MD) simulations. Specifically, we built parameters for the three heme cofactors present in all species of bacterial cytochrome bd-type oxidases (heme b 558 , heme b 595 , and heme d) along with their axial ligands. This data report includes the parameter and library files that can be used with Amber's LEaP program to generate input files for MD simulations using the Amber software package. We also provide the PDB data files of the initial model both by itself and solvated with TIP3P water molecules and counterions.
                      Cover page: Data for molecular dynamics simulations of Escherichia coli cytochrome bd oxidase with the Amber force field
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