Mol. Cell. Biol., Mar 1995, 1137-1143, Vol 15, No. 3
WH Brondyk, CJ McKiernan, KA Fortner, P Stabila, RW Holz and IG Macara
Rab3A is a small, Ras-like GTPase expressed in neuroendocrine cells, in
which it is associated with secretory vesicle membranes and regulates
exocytosis. Using the yeast two-hybrid system, we have identified a rat
brain cDNA encoding a novel 50-kDa protein, which we have named Rabin3,
that interacts with Rab3A and Rab3D but not with other small GTPases
(Rab3C, Rab2, Ran, or Ras). Several independent point mutations in the
effector domain of Rab3A (F51L, V55E, and G56D) which do not alter
nucleotide binding by the GTPase abolish the interaction with Rabin3, while
another mutation (V52A) appears to increase the interaction. These results
demonstrate that the interaction is highly specific. However, a glutathione
S-transferase-Rabin3 fusion protein associates only weakly in vitro with
recombinant Rab3A and possesses no detectable GTPase-activating protein or
nucleotide exchange activity, and Rabin3 overexpressed in adrenal
chromaffin cells has no observable effect on secretion. The protein possess
a sequence characteristic of coiled-coil domains and a second small region
with sequence similarity to a Saccharomyces cerevisiae protein, Sec2p,
Sec2p is essential for constitutive secretion in yeast cells and interacts
with Sec4p, a close relative of the Rab3A GTPase. Rabin3 mRNA and protein
are widely expressed but are particularly abundant in testes.
Copyright © 1995, American Society for Microbiology
Interaction cloning of Rabin3, a novel protein that associates with the Ras-like GTPase Rab3A
Department of Pathology, Vermont Cancer Center, University of Vermont College of Medicine, Burlington 05405-0068.
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