High impact information on YPT6

• The gene, GYP6 (GAP of Ypt6 protein), encodes a protein of 458 amino acids which is highly specific for the Ypt6 protein and shows little or no cross-reactivity with other Ypt/Rab family members or with H-Ras p21 [1].
• We previously identified Sys1p as a high copy number suppressor of Ypt6 GTPase-deficient yeast mutants that are defective in endosome-to-Golgi transport [2].
• A screen for mutants that, like ypt6, specifically impair the growth of imh1 cells led to the identification of RIC1 [3].
• Interestingly, the deletions of GYP1 and YPT6 were synthetic lethal, raising the possibility that at least two distinct pathways are involved in recycling of membrane material [4].
• Based on previous studies with ypt6 deletion mutants, a regulatory role of the GTPase either in protein retrieval to the trans-Golgi network or in forward transport between the endoplasmic reticulum (ER) and early Golgi compartments was proposed [5].

Biological context of YPT6

• Deletion of YPT6 in yeast produces a phenotype showing temperature-sensitive growth and partial missorting of the vacuolar enzyme, carboxypeptidase Y [6].
• Structural and functional analysis of a novel coiled-coil protein involved in Ypt6 GTPase-regulated protein transport in yeast [7].
• However, deletion of SYS1 and/or SYS2 in the ypt6 null mutant enhances defects in vacuolar protein sorting and in cell growth [6].
• The predicted amino acid sequence was highly homologous to the mammalian and yeast counterparts, H.Rab6 and Ryh1/Ypt6, respectively [8].
• Furthermore, we show that the yeast GTPase-activating protein Gyp6, shown to be specifically required to control the GTP hydrolysis of the yeast Ypt6 protein, could interact with tobacco GTP-binding proteins [9].

Anatomical context of YPT6

• In Saccharomyces cerevisiae, the YPT6 gene encodes the homologue of the mammalian Rab6 protein found in the Golgi apparatus [6].
• Mutation of the Rab6 homologue of Saccharomyces cerevisiae, YPT6, inhibits both early Golgi function and ribosome biosynthesis [10].
• In budding yeast Ypt6 is required for recycling of membrane proteins from endosomes back to the Golgi [11].
• A biochemical approach based on the affinity purification of Ypt6:GTP-interacting proteins from yeast cytosol led to the identification of two conserved Ypt6 effectors, the tetrameric VFT complex and Sgm1 [11].

Associations of YPT6 with chemical compounds

• Cloning of extragenic suppressors of the ts allele of YPT6 has revealed two additional proteins that influence the secretory pathway: Ssd1p, a suppressor of many mutations, and Imh1p, which bears some homology to the C-terminal portion of the cytoskeletal proteins integrin and myosin [10].

Regulatory relationships of YPT6

• Here we show that overexpression of YPT1 suppresses the growth and secretion defects of a ypt6 temperature-sensitive (ts) strain [12].

Other interactions of YPT6

• Genetic interaction between YPT6 and YPT1 in Saccharomyces cerevisiae [12].
• SYS1, originally discovered as a multicopy suppressor of defects caused by the absence of the Rab GTPase YPT6, was identified as a multicopy suppressor of ric1Delta [13].
• Whereas protein secretion was not significantly affected in these mutants, the processing of alpha-factor precursor by the Kex2 protease was inhibited, suggesting a function of YPT6 and its null mutant suppressors in transport between the late Golgi and a prevacuolar, endosome-like compartment [6].

References