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- Title
( R)-Cysteate-nitrogen assimilation by Cupriavidus necator H16 with excretion of 3-sulfolactate: a patchwork pathway.
- Authors
Mayer, Jutta; Denger, Karin; Hollemeyer, Klaus; Schleheck, David; Cook, Alasdair
- Abstract
Cupriavidus necator H16 grew exponentially with ( R)-cysteate, a structural analogue of aspartate, as sole source of nitrogen in succinate-salts medium. Utilization of cysteate was quantitative and concomitant with growth and with the excretion of the deaminated product ( R)-sulfolactate, which was identified thoroughly. The deaminative pathway started with transport of ( R)-cysteate into the cell, which we attributed to an aspartate transporter. Transamination to sulfopyruvate involved an aspartate/( R)-cysteate:2-oxoglutarate aminotransferase (Aoa/Coa) and regeneration of the amino group acceptor by NADP-coupled glutamate dehydrogenase. Reduction of sulfopyruvate to ( R)-sulfolactate was catalyzed by a ( S)-malate/( R)-sulfolactate dehydrogenase (Mdh/Sdh). Excretion of the sulfolactate could be attributed to the sulfite/organosulfonate exporter TauE, which was co-encoded and co-expressed, with sulfoacetaldehyde acetyltransferase (Xsc), though Xsc was irrelevant to the current pathway. The metabolic enzymes could be assayed biochemically. Aoa/Coa and Mdh/Sdh were highly enriched by protein separation, partly characterized, and the relevant locus-tags identified by peptide-mass fingerprinting. Finally, RT-PCR was used to confirm the transcription of all appropriate genes. We thus demonstrated that Cupriavidus necator H16 uses a patchwork pathway by recruitment of 'housekeeping' genes and sulfoacetaldehyde-degradative genes to scavenge for ( R)-cysteate-nitrogen.
- Subjects
NITROGEN excretion; SULFONATES; AMINOTRANSFERASE genetics; ACETYLTRANSFERASE genetics; DEHYDROGENASE genetics; REVERSE transcriptase polymerase chain reaction; GEL electrophoresis; SODIUM succinate
- Publication
Archives of Microbiology, 2012, Vol 194, Issue 11, p949
- ISSN
0302-8933
- Publication type
Article
- DOI
10.1007/s00203-012-0825-y