Geobacter sulfurreducens Extracellular Multiheme Cytochrome PgcA Facilitates Respiration to Fe(III) Oxides But Not Electrodes

Structural and Functional Insights of an Unprecedented Multiheme Cytochrome from Geobacter Sulfurreducens

Biophysical Journal ◽

10.1016/j.bpj.2020.11.934 ◽

2021 ◽

Vol 120 (3) ◽

pp. 119a

Author(s):

Tomás M. Fernandes ◽

Leonor Morgado ◽

Filipe Folgosa ◽

Miguel Teixeira ◽

Carlos A. Salgueiro

Keyword(s):

Geobacter Sulfurreducens ◽

Multiheme Cytochrome

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Geobacter sulfurreducensextracellular multiheme cytochrome PgcA facilitates respiration to Fe(III) oxides but not electrodes

10.1101/172775 ◽

2017 ◽

Author(s):

Lori Zacharoff ◽

Dana Morrone ◽

Daniel R. Bond

Keyword(s):

Electron Transfer ◽

Metal Oxides ◽

Solid Phase ◽

Shewanella Oneidensis ◽

Helical Structure ◽

Geobacter Sulfurreducens ◽

Extracellular Electron Transfer ◽

Mineral Surfaces ◽

Electrode Surfaces ◽

Multiheme Cytochrome

AbstractExtracellular cytochromes are hypothesized to facilitate the final steps of electron transfer between the outer membrane of the metal-reducing bacteriumGeobacter sulfurreducensand solid-phase electron acceptors such as metal oxides and electrode surfaces during the course of respiration. The trihemec-type cytochrome PgcA exists in the extracellular space ofG. sulfurreducens, and is one of many multihemec-type cytochromes known to be loosely bound to the bacterial outer surface. Deletion ofpgcAusing a markerless method resulted in mutants unable to transfer electrons to Fe(III) and Mn(IV) oxides; yet the same mutants maintained the ability to respire electrode surfaces and soluble Fe(III) citrate. When expressed and purified fromShewanella oneidensis, PgcA demonstrated a primarily alpha helical structure, three bound hemes, and was processed into a shorter 41 kDa form lacking the lipodomain. Purified PgcA bound Fe(III) oxides, but not magnetite, and when PgcA was added to cell suspensions ofG. sulfurreducens,PgcA accelerated Fe(III) reduction similar to addition of FMN. Addition of soluble PgcA to ∆pgcAmutants also restored Fe(III) reduction. This report highlights a distinction between proteins involved in extracellular electron transfer to metal oxides and poised electrodes, and suggests a specific role for PgcA in facilitating electron transfer at mineral surfaces.

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