The long-term goal of our research is to understand the mechanism of protein import into plant chloroplasts as a model for protein targeting and organelle biogenesis in eukaryotic cells. Organelle identity and development rely on a complex set of intracellular protein trafficking systems that mediate the specific targeting of nuclear-encoded proteins to their proper subcellular compartment. Although protein targeting systems have been described for all organelles, the mechanisms of signal recognition and protein translocation at boundary membranes remain major topics of investigation in cell biology. We have identified a set of chloroplast membrane proteins, the Toc and Tic proteins, that recognize and transport nuclear-encoded proteins into chloroplasts. We are using protein biochemical and cell biological techniques to define the activities of individual Toc/Tic components with the aim of understanding how these complexes selectively recognize chloroplast proteins and transport them across the double-membrane of the chloroplast envelope. A second major goal of our studies is to understand the role of protein import in the development of plants, specifically the process by which plants acquire photosynthetic competence. These studies incorporate molecular genetic techniques in Arabidopsis thaliana to investigate the diversity of Toc-Tic complexes and define the roles of these complexes in the selective import of proteins at different developmental stages.
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Biological conversion assay using Clostridium phytofermentans to estimate plant feedstock quality (with Scott J. Lee, Thomas A. Warnick, Sivakumar Pattathil, Jesus G. Alvelo-Maurosa, Michelle J. Serapiglia, Heather McCormick, Virginia Brown, Naomi F. Young, Lawrence B. Smart, Michael G. Hahn, Jeffrey F. Pedersen, Susan B. Leschine, and Samuel B. Hazen), Biotechnology for Biofuels (2012)
BACKGROUND: There is currently considerable interest in developing renewable sources of energy. One strategy is...
The Molecular Basis for Distinct Pathways for Protein Import into Arabidopsis Chloroplasts (with C. Rounds and H. Inoue), Plant Cell (2010)
The translocons at the outer envelope membrane of chloroplasts (TOCs) initiate the import of thousands...
The Signal Peptide Peptidase Is Required for Pollen Function in Arabidopsis (with S. Han and L. Green), Plant Physiology (2009)
The Signal Peptide Peptidases (SPP) are members of the Intramembrane Cleaving Proteases, which are involved...
The role of GTP binding and hydrolysis at the atToc159 preprotein receptor during protein import into chloroplasts (with F. Wang, B. Agne, and F. Kessler), Journal of Cell Biology (2008)
The majority of nucleus-encoded chloroplast proteins are targeted to the organelle by direct binding to...
Arabidopsis Tic40 Expression in Tobacco Chloroplasts Results in Massive Proliferation of the Inner Envelope Membrane and Upregulation of Associated Proteins (with N. D. Singh, M. Li, S. B. Lee, and H Daniell), Plant Cell (2008)
The chloroplast inner envelope membrane (IM) plays essential roles in lipid synthesis, metabolite transport, and...