title: Structural basis for O2 sensing by the hemerythrin-like domain of a bacterial chemotaxis protein: substrate tunnel and fluxional N terminus.
abstract: The methyl-accepting chemotaxis protein, DcrH, from the anaerobic sulfate-reducing bacterium, Desulfovibrio vulgaris (Hildenborough), has a hemerythrin-like domain, DcrH-Hr, at its C terminus. DcrH-Hr was previously shown to contain a diiron site that binds O2, suggesting an O2-sensing function. X-ray crystal structures of diferric (met-), azido-diferric (azidomet-), and diferrous (deoxy-) DcrH-Hr reveal a "substrate tunnel" distinct from that in invertebrate hemerythrins. This tunnel is proposed to facilitate the rapid autoxidation of oxy-DcrH-Hr and suggests that sensing is triggered by O2 binding and subsequent oxidation of the diferrous active site. The N-terminal loop of DcrH-Hr is highly ordered in both met- and azidomet-DcrH-Hr but is disordered in deoxy-DcrH-Hr. These redox-dependent conformational differences presumably transduce the sensory signal of DcrH-Hr to the neighboring methylation domain in the full-length receptor. Given the putative cytoplasmic localization of its Hr-like O2-sensing domain, DcrH is proposed to serve a role in negative aerotaxis (anaerotaxis).
authors.affiliation: The Ohio State Biophysics Program, The Ohio State University, 484 West 12th Avenue, Columbus, Ohio 43210, USA.
authors.forename: Clara E
authors.initials: CE
authors.lastname: Isaza
authors.forename: Radu
authors.initials: R
authors.lastname: Silaghi-Dumitrescu
authors.forename: Ramesh B
authors.initials: RB
authors.lastname: Iyer
authors.forename: Donald M
authors.initials: DM
authors.lastname: Kurtz
authors.forename: Michael K
authors.initials: MK
authors.lastname: Chan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D001665:Binding Sites; D002633:Chemotaxis / Q000502:physiology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D016969:Desulfovibrio vulgaris / Q000235:genetics / Q000378:metabolism*; D006422:Hemerythrin / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry* / Q000502:physiology; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D006422:Hemerythrin; D010446:Peptide Fragments; D010100:Oxygen