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Unprecedented proximal binding of nitric oxide to heme: implications for guanylate cyclase
Author(s) -
Lawson David M.,
Stevenson Clare E.M.,
Andrew Colin R.,
Eady Robert R.
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.21.5661
Subject(s) - biology , heme , nitric oxide , gucy1a3 , guanylate cyclase , gucy1b3 , biochemistry , enzyme , guanylate cyclase 2c , endocrinology
Microbial cytochromes c ′ contain a 5‐coordinate His‐ligated heme that forms stable adducts with nitric oxide (NO) and carbon monoxide (CO), but not with dioxygen. We report the 1.95 and 1.35 Å resolution crystal structures of the CO‐ and NO‐bound forms of the reduced protein from Alcaligenes xylosoxidans . NO disrupts the His–Fe bond and binds in a novel mode to the proximal face of the heme, giving a 5‐coordinate species. In contrast, CO binds 6‐coordinate on the distal side. A second CO molecule, not bound to the heme, is located in the proximal pocket. Since the unusual spectroscopic properties of cytochromes c ′ are shared by soluble guanylate cyclase (sGC), our findings have potential implications for the activation of sGC induced by the binding of NO or CO to the heme domain.