Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Discovering a new branch in the di-heme cytochrome c peroxidase superfamily (#496)

Ryan V Pham 1 , Takumi A Hawes 1 , Chaoshuang Xia 2 , Kimberly Rizzolo 1 , Sungah Kong 1 , Catherine E Costello 2 , Karen N Allen 1 , Sean J Elliott 1
  1. Department of Chemistry, Boston University, Boston, MA, United States
  2. Department of Biochemistry and Cell Biology, Center for Biomedical Mass Spectrometry, Boston University, Boston, MA, United States

Bacterial cytochrome c peroxidases (bCcP) are part of a massive and largely unknown enzyme superfamily that functionally reduce hydrogen peroxide to water or (unusually) install post-translational modifications. A sequence similarity network of the bCcP/MauG superfamily led to the discovery and subsequent characterization of BthA1 and MbnH2,3 (in Burkholderia thailandensis and Methylosinus trichosporium OB3b respectively). Previously BthA1 was found to be one of two bCcP orthologs in Burkholderia yet possessed an undetermined function. Here we report on the second bCcP family member, BthB, which is always found in the context of a conserved second protein, termed PhosB. In a set of biophysical approaches, we present optical, near-IR, and magnetic spectroscopy (EPR), to corroborate the previously characterized bis-Fe(IV) state necessary for oxidative modifications in MauG4 and MbnH2,3. We identify the impact PhosB on the BthB oxidation state. Protein-protein studies indicate BthB and PhosB bind at low nanomolar affinity. Site-directed mutagenesis of PhosB reveal key catalytic residues for PhosB-based catalysis. Collectively these data are presented as a new model of the MauG-like subfamily of bCcPs in Burkholderia.

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