Details

Autor(en) / Beteiligte

• Pinske, Constanze
• Jaroschinsky, Monique
• Linek, Sabine
• Kelly, Ciarán L.
• Sargent, Frank
• Sawers, R. Gary
• de Boer, P.

Titel

Physiology and Bioenergetics of [NiFe]-Hydrogenase 2-Catalyzed H 2 -Consuming and H 2 -Producing Reactions in Escherichia coli

Ist Teil von

• Journal of bacteriology, 2015-01, Vol.197 (2), p.296-306

Erscheinungsjahr

2015

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• Escherichia coli uptake hydrogenase 2 (Hyd-2) catalyzes the reversible oxidation of H 2 to protons and electrons. Hyd-2 synthesis is strongly upregulated during growth on glycerol or on glycerol-fumarate. Membrane-associated Hyd-2 is an unusual heterotetrameric [NiFe]-hydrogenase that lacks a typical cytochrome b membrane anchor subunit, which transfers electrons to the quinone pool. Instead, Hyd-2 has an additional electron transfer subunit, termed HybA, with four predicted iron-sulfur clusters. Here, we examined the physiological role of the HybA subunit. During respiratory growth with glycerol and fumarate, Hyd-2 used menaquinone/demethylmenaquinone (MQ/DMQ) to couple hydrogen oxidation to fumarate reduction. HybA was essential for electron transfer from Hyd-2 to MQ/DMQ. H 2 evolution catalyzed by Hyd-2 during fermentation of glycerol in the presence of Casamino Acids or in a fumarate reductase-negative strain growing with glycerol-fumarate was also shown to be dependent on both HybA and MQ/DMQ. The uncoupler carbonyl cyanide m -chlorophenylhydrazone (CCCP) inhibited Hyd-2-dependent H 2 evolution from glycerol, indicating the requirement for a proton gradient. In contrast, CCCP failed to inhibit H 2 -coupled fumarate reduction. Although a Hyd-2 enzyme lacking HybA could not catalyze Hyd-2-dependent H 2 oxidation or H 2 evolution in whole cells, reversible H 2 -dependent reduction of viologen dyes still occurred. Finally, hydrogen-dependent dye reduction by Hyd-2 was reversibly inhibited in extracts derived from cells grown in H 2 evolution mode. Our findings suggest that Hyd-2 switches between H 2 -consuming and H 2 -producing modes in response to the redox status of the quinone pool. Hyd-2-dependent H 2 evolution from glycerol requires reverse electron transport.