title: Switchable Redox Chemistry of the Hexameric Tyrosine-Coordinated Heme Protein.
abstract: Hexameric tyrosine-coordinated heme protein HTHP from Silicibacter pomeroyi has been shown to exhibit peroxidase- and catalase-like activity. In the present study, detailed spectroscopic and electrochemical investigations were performed to analyze the redox properties and active site structure of HTHP. Potentiometric titration of HTHP in solution revealed a single redox transition at -0.54 V (vs Ag/AgCl), indicating six structurally identical tyrosine coordinates hemes. Cyclic voltammetry (CV) of immobilized HTHP afforded a distinctly more positive redox potential (-0.17 V) but failed to detect a transition at -0.54 V. Conversely, surface enhanced RR (SERR) spectroscopy provided evidence for both high- and low-potential transitions and for a partial loss of heme in the reduced state. The high-potential CV-active redox transition is attributed to the hemes of the barrel-shaped HTHP in a wheel-like orientation on the surface. Supported by coarse-grained simulations and SERR spectroscopy, the majority of HTHP is concluded to adopt a reverse-disc orientation, accounting for the low-potential transition. In view of the striking similarity of HTHP to the heme carriers HasA or HmbR regarding redox potential, Fe-Tyr ligation, and heme release, we propose heme transport as an alternative or additional function.
authors.affiliation: Institut für Chemie, Sekr. PC14, Technische Universität Berlin , Strasse des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Kielb
authors.affiliation: Institut für Chemie, Sekr. PC14, Technische Universität Berlin , Strasse des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Tillmann
authors.initials: T
authors.lastname: Utesch
authors.affiliation: Institut für Chemie, Sekr. PC14, Technische Universität Berlin , Strasse des 17. Juni 135, D-10623 Berlin, Germany.|Department of Chemistry, Stanford University , Stanford, California 94305-5012, United States.
authors.forename: Jacek
authors.identifier: 0000-0002-2115-4899
authors.initials: J
authors.lastname: Kozuch
authors.affiliation: Institute of Biology, Humboldt Universität Berlin , Philippstrasse 13, D-10115 Berlin, Germany.
authors.forename: Jae-Hun
authors.initials: JH
authors.lastname: Jeoung
authors.affiliation: Institute of Biology, Humboldt Universität Berlin , Philippstrasse 13, D-10115 Berlin, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Dobbek
authors.affiliation: Institut für Chemie, Sekr. PC14, Technische Universität Berlin , Strasse des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Maria Andrea
authors.identifier: 0000-0002-7497-5631
authors.initials: MA
authors.lastname: Mroginski
authors.affiliation: Institut für Chemie, Sekr. PC14, Technische Universität Berlin , Strasse des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Peter
authors.identifier: 0000-0003-1030-5900
authors.initials: P
authors.lastname: Hildebrandt
authors.affiliation: Department of Chemistry and Food Chemistry, Technische Universität Dresden , Zellescher Weg 19, D-01069 Dresden, Germany.
authors.forename: Inez
authors.identifier: 0000-0001-9316-6349
authors.initials: I
authors.lastname: Weidinger
mesh_terms: D020134:Catalytic Domain; D006418:Heme / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D055503:Protein Multimerization; D041902:Rhodobacteraceae / Q000737:chemistry / Q000201:enzymology*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D006420:Hemeproteins; D014443:Tyrosine; D006418:Heme