RT Journal Article SR Electronic T1 Membrane Association of the Arabidopsis ARF Exchange Factor GNOM Involves Interaction of Conserved Domains JF The Plant Cell JO Plant Cell FD American Society of Plant Biologists SP 142 OP 151 DO 10.1105/tpc.107.056515 VO 20 IS 1 A1 Anders, Nadine A1 Nielsen, Michael A1 Keicher, Jutta A1 Stierhof, York-Dieter A1 Furutani, Masahiko A1 Tasaka, Masao A1 Skriver, Karen A1 Jürgens, Gerd YR 2008 UL http://www.plantcell.org/content/20/1/142.abstract AB The GNOM protein plays a fundamental role in Arabidopsis thaliana development by regulating endosome–to–plasma membrane trafficking required for polar localization of the auxin efflux carrier PIN1. GNOM is a family member of large ARF guanine nucleotide exchange factors (ARF-GEFs), which regulate vesicle formation by activating ARF GTPases on specific membranes in animals, plants, and fungi. However, apart from the catalytic exchange activity of the SEC7 domain, the functional significance of other conserved domains is virtually unknown. Here, we show that a distinct N-terminal domain of GNOM mediates dimerization and in addition interacts heterotypically with two other conserved domains in vivo. In contrast with N-terminal dimerization, the heterotypic interaction is essential for GNOM function, as mutations abolishing this 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.