Chen S, Cai H, Park SK, Menon S, Jackson CL, Ferro-Novick S

The TRAPP complexes are multimeric guanine exchange factors for the Rab GTPase Ypt1p. The three complexes (TRAPPI, TRAPPII and TRAPPIII) share a core of common subunits required for GEF activity, as well as unique subunits (Trs130p, Trs120p, Trs85p and Trs65p) that redirect the GEF from the ER-Golgi pathway to different ...

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cellular locations where TRAPP mediates distinct membrane trafficking events. Roles for three of the four unique TRAPP subunits have been described before, however, the role of the TRAPPII-specific subunit Trs65p has remained elusive. Here we demonstrate that Trs65p directly binds to the C-terminus of the Arf1p exchange factor Gea2p and we provide in vivo evidence to show this interaction is physiologically relevant. Gea2p and TRAPPII also bind to the yeast orthologue of the γ subunit of the COPI coat complex (Sec21p), a known Arf1p effector. These and previous findings reveal that TRAPPII is part of an Arf1p GEF-effector loop that appears to play a role in recruiting or stabilizing TRAPPII to membranes. In support of this proposal, we show that TRAPPII is more soluble in an arf1Δ mutant.

Date: Aug. 03, 2011

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