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Siroheme synthase orients substrates for dehydrogenase and chelatase activities in a common active site.
Nat Commun
February 2020
Department of Biological Science and Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
Siroheme is the central cofactor in a conserved class of sulfite and nitrite reductases that catalyze the six-electron reduction of sulfite to sulfide and nitrite to ammonia. In Salmonella enterica serovar Typhimurium, siroheme is produced by a trifunctional enzyme, siroheme synthase (CysG). A bifunctional active site that is distinct from its methyltransferase activity catalyzes the final two steps, NAD-dependent dehydrogenation and iron chelation.
View Article and Find Full Text PDFIdentification of the sirohaem biosynthesis pathway in Staphylococcus aureus.
FEBS J
April 2020
Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
Sirohaem is a modified tetrapyrrole and a key prosthetic group of several enzymes involved in nitrogen and sulfur metabolisms. This work shows that Staphylococcus aureus produces sirohaem through a pathway formed by three independent enzymes. Of the two putative sirohaem synthases encoded in the S.
View Article and Find Full Text PDFStructure of sirohydrochlorin ferrochelatase SirB: the last of the structures of the class II chelatase family.
Dalton Trans
May 2019
Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
The crystal structure of Bacillus subtilis SirB, which catalyses the insertion of Fe2+ into the substrate sirohydrochlorin (SHC) in siroheme biosynthesis, is reported herein as the last of the structures of class II chelatases. The structure of SirB with Co2+ showed that the active site of SirB is located at the N-terminal domain with metal-binding amino acid residues His10, Glu43, and His76, which was also predicted for CbiX, but is distinct from the C-terminal active sites of CbiK and HemH. The biosynthetic model reactions using SirB, Co2+ and uroporphyrin I or protoporphyrin IX as a SHC analogue revealed that SirB showed chelatase activity for uroporphyrin I, but not for protoporphyrin IX.
View Article and Find Full Text PDFPhylogenetic analysis and photoregulation of siroheme biosynthesis genes: uroporphyrinogen III methyltransferase and sirohydrochlorin ferrochelatase of .
Physiol Mol Biol Plants
July 2016
School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067 India.
Uroporphyrinogen III methyl transferase () and Sirohydrochlorin ferrochelatase () are the important genes involved in the biosynthesis of siroheme, the prosthetic group of nitrite reductases (NiR) and sulfite reductases (SiR) involved in nitrogen and sulfur assimilation. Both and could be potential candidate genes targeted for sustainable agriculture especially in N-deficient soil. The phylogenetic analysis revealed that these genes are highly conserved among algae, bryophytes and vascular plants including dicots and monocots.
View Article and Find Full Text PDFDesulfovibrio vulgaris CbiK cobaltochelatase: evolution of a haem binding protein orchestrated by the incorporation of two histidine residues.
Environ Microbiol
January 2017
Instituto de Tecnologia Química e Biológica NOVA, Avenida da República (EAN), Oeiras, 2780-157, Portugal.
The sulfate-reducing bacteria of the Desulfovibrio genus make three distinct modified tetrapyrroles, haem, sirohaem and adenosylcobamide, where sirohydrochlorin acts as the last common biosynthetic intermediate along the branched tetrapyrrole pathway. Intriguingly, D. vulgaris encodes two sirohydrochlorin chelatases, CbiK and CbiK , that insert cobalt/iron into the tetrapyrrole macrocycle but are thought to be distinctly located in the periplasm and cytoplasm respectively.
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