| Abstract Detail
Membrane Transport Wang, Fei [1], Smith, Matthew [2], Agne, Birgit [3], Kessler, Felix [3], Schnell, Danny [5]. The role of GTP in regulating protein import into chloroplasts. Plastids (e.g. chloroplasts) are a diverse group of interrelated organelles that have evolved to perform numerous and diverse metabolic processes within all plant cells, including essential roles in photosynthesis, amino acid and lipid synthesis, and cell signaling. The biogenesis of these organelles and their differentiation into specialized forms in different tissues relies on the import of thousands of nucleus-encoded proteins from the cytoplasm. Protein import is mediated by a group of multimeric membrane protein complexes, designated translocons, which reside within the outer and inner envelope membranes of the organelles. The major pathway for protein import is mediated by interactions between the transit peptide of newly synthesized proteins and receptor components of the translocon at the outer envelope of chloroplasts (Toc). Two Toc GTPases, Toc159 and Toc34, form an integrated transit peptide receptor system. They associate with Toc75, a major component of the Toc membrane channel. The GTPase activity of the two receptors regulates the import process, but the mechanism of this control point is not understood. We have investigated the role of the Toc159 GTPase in Toc assembly and function by examining the effects of two Toc159 GTPase mutants in vivo and in vitro. Our results indicate that the GTPase activity of Toc159 plays an essential role in the assembly of Toc complexes. GTP hydrolysis at the receptor does not appear to be essential for protein import, but likely plays regulatory role at the early stages of import. We will present possible models for the role of GTP in regulating Toc function.
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1 - University of Massachusettes, Amherst, Biochemistry and Molecular Biology, 710 N. Peasant Street, Amherst, MA, 01007, USA
2 - Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5, Department of Biology
3 - Universite de Neuchatel, Rue Emile-Argand 11, 2007 Neuchatel, Switzerl, Institut de Botanique
4 - Universite de Neuchatel, Rue Emile-Argand 11, 2007 Neuchatel, Switzerl, Institut de Botanique
5 - University of Massachusettes, Amherst, MA, 01007, Biochemistry and Molecular Biology
Keywords:
chloroplast protein transport
GTPase
GTP regulation.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P10002
Abstract ID:245 |
