Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Cryo-EM of a bundle-forming multi-heme nanowire in Desulfuromonas soudananensis WTL   (#401)

Holly Petersen 1 , Chi Ho Chan 2 , Daniel R. Bond 2 , Fengbin Wang 1
  1. University of Alabama at Birmingham, Birmingham, ALABAMA, United States
  2. College of Biological Sciences, University of Minnesota , St. Paul, MN, USA

Extracellular electron transfer plays an important role in respiration of electroactive bacteria and geochemical metal cycling. The anaerobic bacterium Geobacter sulfurreducens produces three conductive appendages composed of polymerized multi-heme cytochromes that facilitate long-range transfer of electrons to terminal electron acceptors. As nanowire structures are not available for any other organism in Desulfuromonadia, we investigated Desulfuromonas soudanensis WTL, a bacterium isolated on a poised anode from deep subsurface brine. This bacterium encodes 38 multiheme c-type cytochromes, including three with sequence similarities to the Geobacter OmcE subunit which forms a nanowire in G. sulfurreducens. Here, we present a ~ 3 Å resolution cryo-EM structure of an OmcE-like nanowire with similar heme packing as G. sulfurreducens OmcS and OmcE, but unlike those structures, is not glycosylated. Additionally, the D. soudanensis nanowires bundle in an anti-parallel arrangement never observed in other nanowires. Specific bonds formed between adjacent fibers suggest a mechanism that facilitates electron transfer between cells. This is the first structure of a multi-heme cytochrome nanowire from a G. sulfurreducens relative and contributes to our understanding of heme arrangement conservation and higher-order structures that may affect electron transfer.