Direct electron transfer between frhAGB-encoding hydrogenase and TrxR in a non-methanogenic hyperthermophilic archaeon

Abstract

Previously, a gene cluster homologous to the frhAGB-encoding F420-reducing hydrogenase (Frh) was identified in a non-methanogen Thermococcus onnurineus NA1. The heterotrimeric enzyme complex exhibited hydrogenase activity with methyl viologen, FMN or FAD as electron acceptor, but not with deazaflavin coenzyme F420, implicating that it has a role distinct from that of homologues from methanogens. Herein, we describe that Frh from T. onnurineus NA1 can reduce thioredoxin reductase (TrxR). In the course of understanding the role of TrxR in T. onnurineus NA1, we employed protein-protein interaction tools and some protein bands, of which one band was identified as a protein coded by frhG afterwards, were pulled down with TrxR in the immunoprecipitation experiment using an antibody of TrxR. The relationship between the hydrogenase and TrxR was further investigated, and TrxR could be reduced directly by Frh, coupled with H2 oxidation in the absence of any other electron carriers. Subsequently, the reduced TrxR by Frh relayed cascade of electron transfer to a sulfur response regulator, SurR. The mechanism behind the phenomena will be discussed.en, FMN or FAD as electron acceptor, but not with deazaflavin coenzyme F420, implicating that it has a role distinct from that of homologues from methanogens. Herein, we describe that Frh from T. onnurineus NA1 can reduce thioredoxin reductase (TrxR). In the course of understanding the role of TrxR in T. onnurineus NA1, we employed protein-protein interaction tools and some protein bands, of which one band was identified as a protein coded by frhG afterwards, were pulled down with TrxR in the immunoprecipitation experiment using an antibody of TrxR. The relationship between the hydrogenase and TrxR was further investigated, and TrxR could be reduced directly by Frh, coupled with H2 oxidation in the absence of any other electron carriers. Subsequently, the reduced TrxR by Frh relayed cascade of electron transfer to a sulfur response regulator, SurR. The mechanism behind the phenomena will be discussed.