Journal of Cell Science, Vol 113, Issue 11 1883-1889, Copyright © 2000 by Company of Biologists

JOURNAL ARTICLES

N-terminal targeting of guanine nucleotide exchange factors (GEF) for ADP ribosylation factors (ARF) to the Golgi

SY Lee and B Pohajdak
Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H4J1, Canada.

B2-1 (cytohesin-1) is a member of a group of proteins (including ARNO and ARNO3) that are all of similar size and domain composition. The three proteins contain an N-terminal coiled-coil domain, followed by a Sec7 and a pleckstrin homology (PH) domain. While it is well established that the Sec7 domain functions as a guanine nucleotide exchange factor (GEF) for ADP-ribosylation factors (ARFs) and the PH domain anchors the proteins to membrane phosphoinositols, the function of the N-terminal domain is unknown. Here we show that the N terminus of B2-1 (residues 1-54) is necessary and sufficient to target the protein to the Golgi. The Sec7+PH domains of B2-1 (residues 55-398) are not sufficient for Golgi localization. Further deletion analysis and point mutagenesis indicate that the coiled-coil domain within the N terminus is responsible for Golgi targeting. Furthermore, ARNO and ARNO3 N termini also have the same capability of targeting to the Golgi. We conclude that the N-terminal, (&agr;)-helical, coiled-coil domain is used to target this family of proteins to the Golgi complex.

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