PNNL

Abstract

Photobiologically synthesized hydrogen (H2) gas is an ideal carbon-free biofuel, being both clean to produce and combust. Cyanothece sp. ATCC 51142 is a cyanobacterium capable of performing simultaneous oxygenic photosynthesis and H2 production, a highly perplexing phenomenon because H2 evolving enzymes are O2-sensitive. We employed a chemoproteomic approach to explore the role protein thiol redox dynamics play in the function of the dinitrogenase NifHDK, an enzyme complex capable of hydrogenase activity in aerobic conditions. Our results indicate that NifHDK may act as an emergency electron valve functioning to prevent harmful reactive oxygen species formation, and works in concert with other enzymes to maintain redox homeostasis. These results provide insight into a novel strategy for improving H2 production, as our results suggest that NifHDK senses and responds to intracellular redox conditions, a feature that can potentially be utilized to lock the enzyme complex in a sustained H2-production mode.