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GABA transaminases from Saccharomyces cerevisiae and Arabidopsis thaliana complement function in cytosol and mitochondria
Author(s) -
Cao Juxiang,
Barbosa Jose M.,
Singh Narendra,
Locy Robert D.
Publication year - 2013
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.2962
Subject(s) - biology , saccharomyces cerevisiae , arabidopsis thaliana , cytosol , mitochondrion , complement (music) , function (biology) , biochemistry , microbiology and biotechnology , genetics , yeast , enzyme , gene , mutant , complementation
GABA transaminase (GABA‐T) catalyses the conversion of GABA to succinate semialdehyde (SSA) in the GABA shunt pathway. The GABA‐T from Saccharomyces cerevisiae ( Sc GABA‐TKG) is an α ‐ketoglutarate‐dependent enzyme encoded by the UGA1 gene, while higher plant GABA‐T is a pyruvate/glyoxylate‐dependent enzyme encoded by POP 2 in Arabidopsis thaliana (AtGABA‐T). The GABA‐T from A . thaliana is localized in mitochondria and mediated by an 18‐amino acid N‐terminal mitochondrial targeting peptide predicated by both web‐based utilities TargetP 1.1 and PSORT. Yeast UGA 1 appears to lack a mitochondrial targeting peptide and is localized in the cytosol. To verify this bioinformatic analysis and examine the significance of Sc GABA‐TKG and At GABA‐T compartmentation and substrate specificity on physiological function, expression vectors were constructed to modify both Sc GABA‐TKG and At GABA‐T, so that they express in yeast mitochondria and cytosol. Physiological function was evaluated by complementing yeast Sc GABA‐TKG deletion mutant Δuga1 with At GABA‐T or Sc GABA‐TKG targeted to the cytosol or mitochondria for the phenotypes of GABA growth defect, thermosensitivity and heat‐induced production of reactive oxygen species (ROS). This study demonstrates that At GABA‐T is functionally interchangeable with Sc GABA‐TKG for GABA growth, thermotolerance and limiting production of ROS, regardless of location in mitochondria or cytosol of yeast cells, but At GABA‐T is about half as efficient in doing so as Sc GABA‐TKG. These results are consistent with the hypothesis that pyruvate/glyoxylate‐limited production of NADPH mediates the effect of the GABA shunt in moderating heat stress in Saccharomyces . Copyright © 2013 John Wiley & Sons, Ltd.