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The small GTPase Rho5 of <i>Saccharomyces cerevisiae</i> is required for proper regulation of different signaling pathways, which includes the response to cell wall, osmotic, nutrient, and oxidative stress. We here show that proper in vivo function and intracellular distribution of Rho5 depends on its hypervariable region at the carboxyterminal end, which includes the CAAX box for lipid modification, a preceding polybasic region (PBR) carrying a serine residue, and a 98 amino acid&#8722;specific insertion only present in Rho5 of <i>S. cerevisiae</i> but not in its human homolog Rac1. Results from trapping GFP-Rho5 variants to the mitochondrial surface suggest that the GTPase needs to be activated at the plasma membrane prior to its translocation to mitochondria in order to fulfil its role in oxidative stress response. These findings are supported by heterologous expression of a codon-optimized human <i>RAC1</i> gene, which can only complement a yeast <i>rho5</i> deletion in a chimeric fusion with <i>RHO5</i> sequences that restore the correct spatiotemporal distribution of the encoded protein.