期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 111, 期 7, 页码 2608-2613出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1324240111
关键词
methanogenic archaea; redox regulation; hydrothermal vent; early Earth; evolution
资金
- National Science Foundation [MCB 1020458]
- National Aeronautics and Space Administration [NNX13AI05G]
- US Department of Agriculture Agricultural Research Service Current Research Information System Project [5325-43000-026-00]
- Genetics, Bioinformatics, and Computational Biology Graduate Program
- ARS [813524, ARS-0425203] Funding Source: Federal RePORTER
- Direct For Biological Sciences
- Div Of Molecular and Cellular Bioscience [1020458] Funding Source: National Science Foundation
Thioredoxin (Trx), a small redox protein, controls multiple processes in eukaryotes and bacteria by changing the thiol redox status of selected proteins. The function of Trx in archaea is, however, unexplored. To help fill this gap, we have investigated this aspect in methanarchaea-strict anaerobes that produce methane, a fuel and greenhouse gas. Bioinformatic analyses suggested that Trx is nearly universal in methanogens. Ancient methanogens that produce methane almost exclusively from H-2 plus CO2 carried approximately two Trx homologs, whereas nutritionally versatile members possessed four to eight. Due to its simplicity, we studied the Trx system of Methanocaldococcus jannaschii-a deeply rooted hyperthermophilic methanogen growing only on H-2 plus CO2. The organism carried two Trx homologs, canonical Trx1 that reduced insulin and accepted electrons from Escherichia coli thioredoxin reductase and atypical Trx2. Proteomic analyses with air-oxidized extracts treated with reduced Trx1 revealed 152 potential targets representing a range of processes-including methanogenesis, biosynthesis, transcription, translation, and oxidative response. In enzyme assays, Trx1 activated two selected targets following partial deactivation by O-2, validating proteomics observations: methylenetetrahydromethanopterin dehydrogenase, a methanogenesis enzyme, and sulfite reductase, a detoxification enzyme. The results suggest that Trx assists methanogens in combating oxidative stress and synchronizing metabolic activities with availability of reductant, making it a critical factor in the global carbon cycle and methane emission. Because methanogenesis developed before the oxygenation of Earth, it seems possible that Trx functioned originally in metabolic regulation independently of O2, thus raising the question whether a complex biological system of this type evolved at least 2.5 billion years ago.
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