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  • 8.58
    Impact points
    Light-Activated Regulation of Cofilin Dynamics Using a Photocaged Hydrogen Peroxide Generator.

    Evan W Miller, Nicolas Taulet, Carl S Onak, Elizabeth J New, Julie K Lanselle, Gillian S Smelick, Christopher J Chang

    Journal of the American Chemical Society. 11/2010;

    Hydrogen peroxide (H(2)O(2)) can exert diverse signaling and stress responses within living systems depending on its spatial and temporal dynamics. Here we report a new small-molecule probe for producing H(2)O(2) on demand upon photoactivation and its application for optical regulation of cofilin-ac... [more] Hydrogen peroxide (H(2)O(2)) can exert diverse signaling and stress responses within living systems depending on its spatial and temporal dynamics. Here we report a new small-molecule probe for producing H(2)O(2) on demand upon photoactivation and its application for optical regulation of cofilin-actin rod formation in living cells. This chemical method offers many potential opportunities for dissecting biological roles for H(2)O(2) as well as remote control of cell behavior via H(2)O(2)-mediated pathways.
  • 8.58
    Impact points
    An oxidosqualene cyclase makes numerous products by diverse mechanisms: a challenge to prevailing concepts of triterpene biosynthesis.

    Silvia Lodeiro, Quanbo Xiong, William K Wilson, Mariya D Kolesnikova, Carl S Onak, Seiichi P T Matsuda

    Journal of the American Chemical Society. 10/2007; 129(36):11213-22.

    The genome of the model plant Arabidopsis thaliana encodes 13 oxidosqualene cyclases, 9 of which have been characterized by heterologous expression in yeast. Here we describe another cyclase, baruol synthase (BARS1), which makes baruol (90%) and 22 minor products (0.02-3% each). This represents as m... [more] The genome of the model plant Arabidopsis thaliana encodes 13 oxidosqualene cyclases, 9 of which have been characterized by heterologous expression in yeast. Here we describe another cyclase, baruol synthase (BARS1), which makes baruol (90%) and 22 minor products (0.02-3% each). This represents as many triterpenes as have been reported for all other Arabidopsis cyclases combined. By accessing an extraordinary repertoire of mechanistic pathways, BARS1 makes numerous skeletal types and deprotonates the carbocation intermediates at 14 different sites around rings A, B, C, D, and E. This undercurrent of structural and mechanistic diversity in a superficially accurate enzyme is incompatible with prevailing concepts of triterpene biosynthesis, which posit tight control over the mechanistic pathway through cation-pi interactions, with a single proton acceptor in a hydrophobic active site. Our findings suggest that mechanistic diversity is the default for triterpene biosynthesis and that product accuracy results from exclusion of alternative pathways.

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