title: Introducing a 2-His-1-Glu nonheme iron center into myoglobin confers nitric oxide reductase activity.
abstract: A conserved 2-His-1-Glu metal center, as found in natural nonheme iron-containing enzymes, was engineered into sperm whale myoglobin by replacing Leu29 and Phe43 with Glu and His, respectively (swMb L29E, F43H, H64, called Fe(B)Mb(-His)). A high resolution (1.65 A) crystal structure of Cu(II)-CN(-)-Fe(B)Mb(-His) was determined, demonstrating that the unique 2-His-1-Glu metal center was successfully created within swMb. The Fe(B)Mb(-His) can bind Cu, Fe, or Zn ions, with both Cu(I)-Fe(B)Mb(-His) and Fe(II)-Fe(B)Mb(-His) exhibiting nitric oxide reductase (NOR) activities. Cu dependent NOR activity was significantly higher than that of Fe in the same metal binding site. EPR studies showed that the reduction of NO to N(2)O catalyzed by these two enzymes resulted in different intermediates; a five-coordinate heme-NO species was observed for Cu(I)-Fe(B)Mb(-His) due to the cleavage of the proximal heme Fe-His bond, while Fe(II)-Fe(B)Mb(-His) remained six-coordinate. Therefore, both the metal ligand, Glu29, and the metal itself, Cu or Fe, play crucial roles in NOR activity. This study presents a novel protein model of NOR and provides insights into a newly discovered member of the NOR family, gNOR.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Ying-Wu
authors.initials: YW
authors.lastname: Lin
authors.forename: Natasha
authors.initials: N
authors.lastname: Yeung
authors.forename: Yi-Gui
authors.initials: YG
authors.lastname: Gao
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Miner
authors.forename: Lanyu
authors.initials: L
authors.lastname: Lei
authors.forename: Howard
authors.initials: H
authors.lastname: Robinson
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009211:Myoglobin; D007501:Iron; D010088:Oxidoreductases; C034747:nitric-oxide reductase