Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Vendredi 11 janvier 2008
Amphi 208 (Cœur d’Ecole) à 13h30
Interaction between conserved domains is essential for function of the Arabidopsis ARF exchange factor GNOM
ARF GTPases are essential regulators of membrane trafficking in eukaryotes. They are spatially and temporally controlled by the activity of GDP/GTP exchange factors (GEFs), that reversibly associate with specific membranes. Common to all groups of eukaryotes is the family of large multi-domain containing ARF-GEFs, however, virtually nothing is known about mechanisms of their membrane association or regulation of their activity. The large ARF-GEF GNOM is a central regulator of Arabidopsis development by mediating trafficking from endosomal compartments to the plasma membrane, thus establishing the polar localization of the auxin efflux carrier PIN1. We used GNOM to investigate the role of conserved, but yet uncharacterized domains in regulating ARF-GEF function. Our data show that a distinct domain of GNOM mediates both N-terminal dimerization and interaction with other conserved domains in vivo. In contrast to N-terminal dimerization, the latter interaction is essential for function, as mutations abolishing the interaction inactivate the GNOM protein and compromise its membrane association. Our results suggest a general model of large ARF-GEF function in which regulated changes in protein conformation control membrane association of the exchange factor and thus activation of ARFs.
Contact : Grégory Vert