Bio

Honors & Awards


  • Graduate Research Fellowship, National Science Foundation (2014-2017)

Education & Certifications


  • B.A., Reed College, Biochemistry & Molecular Biology (2011)

Research & Scholarship

Current Research and Scholarly Interests


I'm currently studying the mechanism of translation initiation by the HCV IRES.

Lab Affiliations


Publications

All Publications


  • Dynamics of IRES-mediated translation. Philosophical transactions of the Royal Society of London. Series B, Biological sciences Johnson, A. G., Grosely, R., Petrov, A. N., Puglisi, J. D. 2017; 372 (1716)

    Abstract

    Viral internal ribosome entry sites (IRESs) are unique RNA elements, which use stable and dynamic RNA structures to recruit ribosomes and drive protein synthesis. IRESs overcome the high complexity of the canonical eukaryotic translation initiation pathway, often functioning with a limited set of eukaryotic initiation factors. The simplest types of IRESs are typified by the cricket paralysis virus intergenic region (CrPV IGR) and hepatitis C virus (HCV) IRESs, both of which independently form high-affinity complexes with the small (40S) ribosomal subunit and bypass the molecular processes of cap-binding and scanning. Owing to their simplicity and ribosomal affinity, the CrPV and HCV IRES have been important models for structural and functional studies of the eukaryotic ribosome during initiation, serving as excellent targets for recent technological breakthroughs in cryogenic electron microscopy (cryo-EM) and single-molecule analysis. High-resolution structural models of ribosome : IRES complexes, coupled with dynamics studies, have clarified decades of biochemical research and provided an outline of the conformational and compositional trajectory of the ribosome during initiation. Here we review recent progress in the study of HCV- and CrPV-type IRESs, highlighting important structural and dynamics insights and the synergy between cryo-EM and single-molecule studies.This article is part of the themed issue 'Perspectives on the ribosome'.

    View details for DOI 10.1098/rstb.2016.0177

    View details for PubMedID 28138065

  • Identification of Selective Inhibitors of the Plasmodium falciparum Hexose Transporter PfHT by Screening Focused Libraries of Anti-Malarial Compounds. PloS one Ortiz, D., Guiguemde, W. A., Johnson, A., Elya, C., Anderson, J., Clark, J., Connelly, M., Yang, L., Min, J., Sato, Y., Guy, R. K., Landfear, S. M. 2015; 10 (4): e0123598

    Abstract

    Development of resistance against current antimalarial drugs necessitates the search for novel drugs that interact with different targets and have distinct mechanisms of action. Malaria parasites depend upon high levels of glucose uptake followed by inefficient metabolic utilization via the glycolytic pathway, and the Plasmodium falciparum hexose transporter PfHT, which mediates uptake of glucose, has thus been recognized as a promising drug target. This transporter is highly divergent from mammalian hexose transporters, and it appears to be a permease that is essential for parasite viability in intra-erythrocytic, mosquito, and liver stages of the parasite life cycle. An assay was developed that is appropriate for high throughput screening against PfHT based upon heterologous expression of PfHT in Leishmania mexicana parasites that are null mutants for their endogenous hexose transporters. Screening of two focused libraries of antimalarial compounds identified two such compounds that are high potency selective inhibitors of PfHT compared to human GLUT1. Additionally, 7 other compounds were identified that are lower potency and lower specificity PfHT inhibitors but might nonetheless serve as starting points for identification of analogs with more selective properties. These results further support the potential of PfHT as a novel drug target.

    View details for DOI 10.1371/journal.pone.0123598

    View details for PubMedID 25894322

  • Dyotropic Rearrangements of Fused Tricyclic beta-Lactones: Application to the Synthesis of (-)-Curcumanolide A and (-)-Curcumalactone JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Leverett, C. A., Purohit, V. C., Johnson, A. G., Davis, R. L., Tantillo, D. J., Romo, D. 2012; 134 (32): 13348-13356

    Abstract

    Dyotropic rearrangements of fused, tricyclic ?-lactones are described that proceed via unprecedented stereospecific, 1,2-acyl migrations delivering bridged, spiro-?-butyrolactones. A unique example of this dyotropic process involves a fused bis-lactone possessing both ?- and ?-lactone moieties which enabled rapid access to the core structures of curcumanolide A and curcumalactone. Our current mechanistic understanding of the latter dyotropic process, based on computational studies, is also described. Other key transformations in the described divergent syntheses of (-)-curcumanolide A and (-)-curcumalactone from a common intermediate (11 and 12 steps from 2-methyl-1,3-cyclopentanedione, respectively), include a catalytic, asymmetric nucleophile (Lewis base)-catalyzed aldol-lactonization (NCAL) leading to a tricyclic ?-lactone, a Baeyer-Villiger oxidation in the presence of a ?-lactone, and highly facial-selective and stereocomplementary reductions of an intermediate spirocyclic enoate. The described dyotropic rearrangements significantly alter the topology of the starting tricyclic ?-lactone, providing access to complex spirocyclic cyclopentyl-?-lactones and bis-?-lactones in a single synthetic operation.

    View details for DOI 10.1021/ja303414a

    View details for Web of Science ID 000307487200039

    View details for PubMedID 22853802