Genome Sequence, Proteome Profile, and Identification of a Multiprotein Reductive Dehalogenase Complex in Dehalogenimonas alkenigignens Strain BRE15M

Bacteria
of the genus Dehalogenimonas respire
with vicinally halogenated alkanes via dihaloelimination.
We aimed to describe involved proteins and their supermolecular organization.
Metagenomic sequencing of a Dehalogenimonas-containing culture resulted in a 1.65 Mbp draft genome of Dehalogenimonas alkenigignens strain BRE15M. It contained
31 full-length reductive dehalogenase homologous genes (rdhA), but only eight had cognate rdhB gene coding for
membrane-anchoring proteins. Shotgun proteomics of cells grown with
1,2-dichloropropane as an electron acceptor identified 1152 proteins
representing more than 60% of the total proteome. Ten RdhA proteins
were detected, including a DcpA ortholog, which was the strongest
expressed RdhA. Blue native gel electrophoresis
(BNE) demonstrating maximum activity was localized in a protein complex
of 146–242 kDa. Protein mass spectrometry revealed the presence
of DcpA, its membrane-anchoring protein DcpB, two hydrogen uptake
hydrogenase subunits (HupL and HupS), an iron–sulfur protein
(HupX), and subunits of a redox protein with a molybdopterin-binding
motif (OmeA and OmeB) in the complex. BNE after protein solubilization
with different detergent concentrations revealed no evidence for an
interaction between the putative respiratory electron input module
(HupLS) and the OmeA/OmeB/HupX module. All detected RdhAs comigrated
with the organohalide respiration complex. Based on genomic and proteomic
analysis, we propose quinone-independent respiration in Dehalogenimonas.