title: A unique Ni2+ -dependent and methylglyoxal-inducible rice glyoxalase I possesses a single active site and functions in abiotic stress response.
abstract: The glyoxalase system constitutes the major pathway for the detoxification of metabolically produced cytotoxin methylglyoxal (MG) into a non-toxic metabolite D-lactate. Glyoxalase I (GLY I) is an evolutionarily conserved metalloenzyme requiring divalent metal ions for its activity: Zn(2+) in the case of eukaryotes or Ni(2+) for enzymes of prokaryotic origin. Plant GLY I proteins are part of a multimember family; however, not much is known about their physiological function, structure and metal dependency. In this study, we report a unique GLY I (OsGLYI-11.2) from Oryza sativa (rice) that requires Ni(2+) for its activity. Its biochemical, structural and functional characterization revealed it to be a monomeric enzyme, possessing a single Ni(2+) coordination site despite containing two GLY I domains. The requirement of Ni(2+) as a cofactor by an enzyme involved in cellular detoxification suggests an essential role for this otherwise toxic heavy metal in the stress response. Intriguingly, the expression of OsGLYI-11.2 was found to be highly substrate inducible, suggesting an important mode of regulation for its cellular levels. Heterologous expression of OsGLYI-11.2 in Escherichia coli and model plant Nicotiana tabacum (tobacco) resulted in improved adaptation to various abiotic stresses caused by increased scavenging of MG, lower Na(+) /K(+) ratio and maintenance of reduced glutathione levels. Together, our results suggest interesting links between MG cellular levels, its detoxification by GLY I, and Ni(2+) - the heavy metal cofactor of OsGLYI-11.2, in relation to stress response and adaptation in plants.
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
authors.forename: Ananda
authors.initials: A
authors.lastname: Mustafiz
authors.forename: Ajit
authors.initials: A
authors.lastname: Ghosh
authors.forename: Amit K
authors.initials: AK
authors.lastname: Tripathi
authors.forename: Charanpreet
authors.initials: C
authors.lastname: Kaur
authors.forename: Akshay K
authors.initials: AK
authors.lastname: Ganguly
authors.forename: Neel S
authors.initials: NS
authors.lastname: Bhavesh
authors.forename: Jayant K
authors.initials: JK
authors.lastname: Tripathi
authors.forename: Ashwani
authors.initials: A
authors.lastname: Pareek
authors.forename: Sudhir K
authors.initials: SK
authors.lastname: Sopory
authors.forename: Sneh L
authors.initials: SL
authors.lastname: Singla-Pareek
mesh_terms: D020134:Catalytic Domain; D004926:Escherichia coli / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007791:Lactoylglutathione Lyase / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D012275:Oryza / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary; D013312:Stress, Physiological; D014026:Nicotiana / Q000235:genetics
chemical_list: D009532:Nickel; D007791:Lactoylglutathione Lyase
keywords: Oryza sativa L; abiotic stresses; glutathione; glyoxalase I; methylglyoxal; nickel-dependent enzyme; stress response; stress tolerance