title: Molecular basis for nitric oxide dynamics and affinity with Alcaligenes xylosoxidans cytochrome c.
abstract: The bacterial heme protein cytochrome ć from Alcaligenes xylosoxidans (AXCP) reacts with nitric oxide (NO) to form a 5-coordinate ferrous nitrosyl heme complex. The crystal structure of ferrous nitrosyl AXCP has previously revealed that NO is bound in an unprecedented manner on the proximal side of the heme. To understand how the protein structure of AXCP controls NO dynamics, we performed absorption and Raman time-resolved studies at the heme level as well as a molecular computational dynamics study at the entire protein structure level. We found that after NO dissociation from the heme iron, the structure of the proximal heme pocket of AXCP confines NO close to the iron so that an ultrafast (7 ps) and complete (99 +/- 1%) geminate rebinding occurs, whereas the proximal histidine does not rebind to the heme iron on the timescale of NO geminate rebinding. The distal side controls the initial NO binding, whereas the proximal heme pocket controls its release. These dynamic properties allow the trapping of NO within the protein core and represent an extreme behavior observed among heme proteins.
authors.affiliation: Ecole Polytechnique, Laboratoire d'Optique et Biosciences, CNRS UMR 7645, 91128 Palaiseau Cedex, France; BioMoCeTi, CNRS UMR 7033, University Pierre and Marie Curie, Genopole Campus 1, 91030 Evry, France.
authors.forename: Sergei G
authors.initials: SG
authors.lastname: Kruglik
authors.affiliation: Ecole Polytechnique, Laboratoire d'Optique et Biosciences, CNRS UMR 7645, 91128 Palaiseau Cedex, France; INSERM, U696, 91128 Palaiseau Cedex, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Lambry
authors.affiliation: Ecole Polytechnique, Laboratoire d'Optique et Biosciences, CNRS UMR 7645, 91128 Palaiseau Cedex, France.
authors.forename: Simona
authors.initials: S
authors.lastname: Cianetti
authors.affiliation: Ecole Polytechnique, Laboratoire d'Optique et Biosciences, CNRS UMR 7645, 91128 Palaiseau Cedex, France; INSERM, U696, 91128 Palaiseau Cedex, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Martin
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich NR4 7UH, United Kingdom, and.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Eady
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Oregon University, La Grande, Oregon 97850.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Andrew
authors.affiliation: Ecole Polytechnique, Laboratoire d'Optique et Biosciences, CNRS UMR 7645, 91128 Palaiseau Cedex, France; INSERM, U696, 91128 Palaiseau Cedex, France. Electronic address: michel.negrerie@polytechnique.fr.
authors.forename: Michel
authors.initials: M
authors.lastname: Negrerie
mesh_terms: D000421:Alcaligenes / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D045305:Cytochromes c' / Q000737:chemistry*; D006418:Heme / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013059:Spectrum Analysis, Raman
chemical_list: D001426:Bacterial Proteins; D045305:Cytochromes c'; D009569:Nitric Oxide; D006418:Heme