期刊
FRONTIERS IN MICROBIOLOGY
卷 11, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2020.578209
关键词
dissimilatory sulfate reduction; dissimilatory sulfur oxidation; DsrAB; DsrL; sulfur metabolism; sulfite reductase; NAD(P)H
类别
资金
- Deutsche Forschungsgemeinschaft [Da 351/6-2]
- Fundacao para a Ciencia e Tecnologia (Portugal) [PTDC/BIA-BQM/29118/2017, SFRH/BPD/79823/2011, PTDC/BIA-MIC/6512/2014]
- Fundacao para a Ciencia e Tecnologia (Portugal) through R&D unit MOSTMICRO-ITQB [UIDB/04612/2020, UIDP/04612/2020]
- Fundação para a Ciência e a Tecnologia [PTDC/BIA-BQM/29118/2017, SFRH/BPD/79823/2011, PTDC/BIA-MIC/6512/2014] Funding Source: FCT
DsrAB-type dissimilatory sulfite reductase is a key enzyme of microbial sulfur-dependent energy metabolism. Sulfur oxidizers also contain DsrL, which is essential for sulfur oxidation in Allochromatium vinosum. This NAD(P)H oxidoreductase acts as physiological partner of oxidative-type rDsrAB. Recent analyses uncovered that DsrL is not confined to sulfur oxidizers but also occurs in (probable) sulfate/sulfur-reducing bacteria. Here, phylogenetic analysis revealed a separation into two major branches, DsrL-1, with two subgroups, and DsrL-2. When present in organisms with reductive-type DsrAB, DsrL is of type 2. In the majority of cases oxidative-type rDsrAB occurs with DsrL-1 but combination with DsrL-2-type enzymes is also observed. Three model DsrL proteins, DsrL-1A and DsrL-1B from the sulfur oxidizers A. vinosum and Chlorobaculum tepidum, respectively, as well as DsrL-2 from thiosulfate- and sulfur-reducing Desulfurella amilsii were kinetically characterized. DaDsrL-2 is active with NADP(H) but not with NAD(H) which we relate to a conserved YRR-motif in the substrate-binding domains of all DsrL-2 enzymes. In contrast, AvDsrL-1A has a strong preference for NAD(H) and the CtDsrL-1B enzyme is completely inactive with NADP(H). Thus, NAD(+) as well as NADP(+) are suitable in vivo electron acceptors for rDsrABL-1-catalyzed sulfur oxidation, while NADPH is required as electron donor for sulfite reduction. This observation can be related to the lower redox potential of the NADPH/NADP(+) than the NADH/NAD(+) couple under physiological conditions. Organisms with a rdsrAB and dsrL-1 gene combination can be confidently identified as sulfur oxidizers while predictions for organisms with other combinations require much more caution and additional information sources.
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