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Kessler, Félix

Nom
Kessler, Félix
Affiliation principale
Fonction
Professeur ordinaire
Email
felix.kessler@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/320

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  • Publication
    Métadonnées seulement
    AtTic110 functions as a scaffold for coordinating the stromal events of protein import into chloroplasts
    (2003)
    Inaba, Takehito
    ;
    Li, Ming
    ;
    Alvarez-Huerta, Mayte
    ;
    Kessler, Félix 
    ;
    Schnell, Danny
    The translocon of the inner envelope membrane of chloroplasts ( Tic) mediates the late events in the translocation of nucleus-encoded preproteins into chloroplasts. Tic110 is a major integral membrane component of active Tic complexes and has been proposed to function as a docking site for translocation-associated stromal factors and as a component of the protein-conducting channel. To investigate the various proposed functions of Tic110, we have investigated the structure, topology, and activities of a 97.5-kDa fragment of Arabidopsis Tic110 ( atTic110) lacking only the amino-terminal transmembrane segments. The protein was expressed both in Escherichia coli and Arabidopsis as a stable, soluble protein with a high alpha-helical content. Binding studies demonstrate that a region of the at-Tic110-soluble domain selectively associates with chloroplast preproteins at the late stages of membrane translocation. These data support the hypothesis that the bulk of Tic110 extends into the chloroplast stroma and suggest that the domain forms a docking site for preproteins as they emerge from the Tic translocon.
  • Publication
    Métadonnées seulement
    A GTPase gate for protein import into chloroplasts
    (2002)
    Kessler, Félix 
    ;
    Schnell, Danny
    Protein import into chloroplasts is regulated by the binding and hydrolysis of GTP at two homologous GTPases, Toc34 and Toc159. The crystal structure of the Toc34 GTP-binding domain suggests that GTP-regulated dimerization of the Toc GTPase domains controls the targeting and translocation of preproteins at the chloroplast envelope.
  • Publication
    Métadonnées seulement
    Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membrane
    (2002)
    Bauer, Jörg
    ;
    Hiltbrunner, Andreas
    ;
    Weibel, Petra 
    ;
    Vidi, Pierre-Alexandre
    ;
    Alvarez-Huerta, Mayte
    ;
    Smith, Matthew
    ;
    Schnell, Danny
    ;
    Kessler, Félix 
    Two homologous GTP-binding proteins, atToc33 and atToc159, control access of cytosolic precursor proteins to the chloroplast. atToc33 is a constitutive outer chloroplast membrane protein, whereas the precursor receptor atToc159 also exists in a soluble, cytosolic form. This suggests that atToc159 may be able to switch between a soluble and an integral membrane form. By transient expression of GFP fusion proteins, mutant analysis, and biochemical experimentation, we demonstrate that the GTP-binding domain regulates the targeting of cytosolic atToc159 to the chloroplast and mediates the switch between cytosolic and integral membrane forms. Mutant atToc159, unable to bind GTP, does not reinstate a green phenotype in an albino mutant (ppi2) lacking endogenous atToc159, remaining trapped in the cytosol. Thus, the function of atToc159 in chloroplast biogenesis is dependent on an intrinsic GTP-regulated switch that controls localization of the receptor to the chloroplast envelope.
  • Publication
    Métadonnées seulement
    Targeting of an abundant cytosolic form of the protein import receptor at Toc159 to the outer chloroplast membrane
    (2001)
    Hiltbrunner, Andreas
    ;
    Bauer, Jörg
    ;
    Vidi, Pierre-Alexandre
    ;
    Infanger, Sibylle
    ;
    Weibel, Petra 
    ;
    Hohwy, Morten
    ;
    Kessler, Félix 
    Chloroplast biogenesis requires the large-scale import of cytosolically synthesized precursor proteins. A trimeric translocon (Toc complex) containing two homologous, GTP-binding proteins (atToc33 and atToc159) and a channel protein (atToc75) facilitates protein translocation across the outer envelope membrane. The mechanisms governing function and assembly of the Toc complex are not yet understood. This study demonstrates that atToc159 and its pea orthologue exist in an abundant, previously unrecognized soluble form, and partition between cytosol-containing soluble fractions and the chloroplast outer membrane. We show that soluble atToc159 binds directly to the cytosolic domain of atToc33 in a homotypic interaction, contributing to the integration of atToc159 into the chloroplast outer membrane. The data suggest that the function of the Toc complex involves switching of at Toc159 between a soluble and an integral membrane form.