Switchable Redox Chemistry of the Hexameric Tyrosine-Coordinated Heme Protein

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Patrycja Kielb - , Technical University of Berlin (Author)
  • Tillmann Utesch - , Technical University of Berlin (Author)
  • Jacek Kozuch - , Technical University of Berlin, Stanford University (Author)
  • Jae Hun Jeoung - , Humboldt University of Berlin (Author)
  • Holger Dobbek - , Humboldt University of Berlin (Author)
  • Maria Andrea Mroginski - , Technical University of Berlin (Author)
  • Peter Hildebrandt - , Technical University of Berlin (Author)
  • Inez Weidinger - , Chair of Electrochemistry (Author)

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.

Details

Original languageEnglish
Pages (from-to)3955-3964
Number of pages10
JournalJournal of Physical Chemistry B
Volume121
Issue number16
Publication statusPublished - 27 Apr 2017
Peer-reviewedYes

External IDs

PubMed 28383909