title: Expanding the paradigm of thiol redox in the thermophilic root of life.
abstract: BACKGROUND
  The current paradigm of intracellular redox chemistry maintains that cells establish a reducing environment maintained by a pool of small molecule and protein thiol to protect against oxidative damage. This strategy is conserved in mesophilic organisms from all domains of life, but has been confounded in thermophilic organisms where evidence suggests that intracellular proteins have abundant disulfides.
  
  
  METHODS
  Chemical labeling and 2-dimensional gel electrophoresis were used to capture disulfide bonding in the proteome of the model thermophile Sulfolobus solfataricus. The redox poise of the metabolome was characterized using both chemical labeling and untargeted liquid chromatography mass spectrometry. Gene annotation was undertaken using support vector machine based pattern recognition.
  
  
  RESULTS
  Proteomic analysis indicated the intracellular protein thiol of S. solfataricus was primarily in the disulfide form. Metabolic characterization revealed a lack of reduced small molecule thiol. Glutathione was found primarily in the oxidized state (GSSG), at relatively low concentration. Combined with genetic analysis, this evidence shows that pathways for synthesis of glutathione do exist in the archaeal domain.
  
  
  CONCLUSIONS
  In observed thermophilic organisms, thiol abundance and redox poise suggest that this system is not directly utilized for protection against oxidative damage. Instead, a more oxidized intracellular environment promotes disulfide bonding, a critical adaptation for protein thermostability.
  
  
  CONCLUSIONS
  Based on the placement of thermophilic archaea close to the last universal common ancestor in rRNA phylogenies, we hypothesize that thiol-based redox systems are derived from metabolic pathways originally tasked with promoting protein stability.
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
authors: Joshua
authors: J
authors: Heinemann
authors: Timothy
authors: T
authors: Hamerly
authors: Walid S
authors: WS
authors: Maaty
authors: Navid
authors: N
authors: Movahed
authors: Joseph D
authors: JD
authors: Steffens
authors: Benjamin D
authors: BD
authors: Reeves
authors: Jonathan K
authors: JK
authors: Hilmer
authors: Jesse
authors: J
authors: Therien
authors: Paul A
authors: PA
authors: Grieco
authors: John W
authors: JW
authors: Peters
authors: Brian
authors: B
authors: Bothner
mesh_terms: D000222:Adaptation, Physiological; D002853:Chromatography, Liquid; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D006358:Hot Temperature; D055442:Metabolome; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D020543:Proteome / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D048229:Sulfolobus solfataricus / Q000378:metabolism*
chemical_list: D004220:Disulfides; D011506:Proteins; D020543:Proteome; D009249:NADP; D005978:Glutathione; D003545:Cysteine
keywords: Disulfide; Glutathione; Metabolomics; Proteomics; Thermophile; Thiol