Reversible conversion of coenzyme F420 to the 8-OH-AMP and 8-OH-GMP esters,F390-A and F390-G,on oxygen exposure and reestablishment of anaerobiosis in Methanobacterium thermoautotrophicum |
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| Authors: | Andreas Kiener William H Orme-Johnson Christopher T Walsh |
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| Institution: | (1) Department of Biology, Massachusetts Institute of Technology, 02139 Cambridge, MA, USA;(2) Department of Chemistry, Massachusetts Institute of Technology, 02139 Cambridge, MA, USA;(3) Present address: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 02115 Boston, MA, USA |
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| Abstract: | Intracellular levels of F390 (AMP and GMP adducts of the 5-deazaflavin cofactor F420) in Methanobacterium thermoautotrophicum were analysed after gasing fermenter cultures with several consecutive cycles of substrate gas and gas mixtures containing 5% oxygen. No F390 was detected in growing cells, hydrogen starved cells and CO2 starved cells prior to O2 contamination. Also, no F390 was found in hydrogen depleted cells after O2 treatment. Exposure of exponentially growing cells and CO2 starved cells to oxygen lead to the formation of F390 species; the increase in the detected amount of F390 was coupled to a decrease of the F420 level. As soon as anaerobiosis was reestablished F390 cofactors were degraded and growth proceeded. Independent of the physiological condition of Methanobacterium thermoautotrophicum methanopterin was formed upon O2 exposure. After normal growth conditions were restored the level of detected methanopterin decreased again. |
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| Keywords: | 5-Deazaflavin Nucleotidyl-5-deazaflavin Methanopterin Oxygen sensitivity |
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