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PDBsum entry 6p7c
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References listed in PDB file
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Key reference
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Title
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Siroheme synthase orients substrates for dehydrogenase and chelatase activities in a common active site.
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Authors
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J.M.Pennington,
M.Kemp,
L.Mcgarry,
Y.Chen,
M.E.Stroupe.
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Ref.
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Nat Commun, 2020,
11,
864.
[DOI no: ]
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PubMed id
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Abstract
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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.
How this active site performs such different chemistries is unknown. Here, we
report the structures of CysG bound to precorrin-2, the initial substrate;
sirohydrochlorin, the dehydrogenation product/chelation substrate; and a
cobalt-sirohydrochlorin product. We identified binding poses for all three
tetrapyrroles and tested the roles of specific amino acids in both activities to
give insights into how a bifunctional active site catalyzes two different
chemistries and acts as an iron-specific chelatase in the final step of siroheme
synthesis.
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