The glutamyl tail length of the cofactor F420 in the methanogenic Archaea Methanosarcina thermophila and Methanoculleus thermophilus

Abstract

The cofactor F420 is synthesized by many different organisms and as a redox cofactor, it plays a crucial role in the redox reactions of catabolic and biosynthetic metabolic pathways. It consists of a deazaflavin structure, which is linked via lactate to an oligoglutamate chain, that can vary in length. In the present study, the methanogenic Archaea Methanosarcina thermophila and Methanoculleus thermophilus were cultivated on different carbon sources and their coenzyme F420 composition has been assayed by reversed-phase ion-pair high-performance liquid chromatography with fluorometric detection regarding both, overall cofactor F420 production and distribution of F420 glutamyl tail length. In Methanosarcina thermophila cultivated on methanol, acetate, and a mixture of acetate and methanol, the most abundant cofactors were F420-5 and F420-4, whereby the last digit refers to the number of expressed glutamyl rests. By contrast, in the obligate CO2 reducing Methanoculleus thermophilus the most abundant cofactors were F420-3 and F420-4. In Methanosarcina thermophila, the relative proportions of the expressed F420 tail length changed during batch growth on all three carbon sources. Over time F420-3 and F420-4 decreased while F420-5 and F420-6 increased in their relative proportion in comparison to total F420 content. In contrast, in Methanoculleus thermophilus the relative abundance of the different F420 cofactors remained stable. It was also possible to differentiate the two methanogenic Archaea based on the glutamyl tail length of the cofactor F420. The cofactor F420-5 in concentrations >2% could only be assigned to Methanosarcina thermophila. In all four variants a trend for a positive correlation between the DNA concentration and the total concentration of the cofactor could be shown. Except for the variant Methanosarcinathermophila with acetate as sole carbon source the same could be shown between the concentration of the mcrA gene copy number and the total concentration of the cofactor.