Site-directed mutagenesis of the Anabaena sp. strain PCC 7120 nitrogenase active site to increase photobiological hydrogen production.

ABSTRACT: Cyanobacteria use sunlight and water to produce hydrogen gas (H?), which is potentially useful as a clean and renewable biofuel. Photobiological H? arises primarily as an inevitable by-product of N? fixation by nitrogenase, an oxygen-labile enzyme typically containing an iron-molybdenum cofactor (FeMo-co) active site. In Anabaena sp. strain 7120, the enzyme is localized to the microaerobic environment of heterocysts, a highly differentiated subset of the filamentous cells. In an effort to increase H? production by this strain, six nitrogenase amino acid residues predicted to reside within 5 Å of the FeMo-co were mutated in an attempt to direct electron flow selectively toward proton reduction in the presence of N?. Most of the 49 variants examined were deficient in N?-fixing growth and exhibited decreases in their in vivo rates of acetylene reduction. Of greater interest, several variants examined under an N? atmosphere significantly increased their in vivo rates of H? production, approximating rates equivalent to those under an Ar atmosphere, and accumulated high levels of H? compared to the reference strains. These results demonstrate the feasibility of engineering cyanobacterial strains for enhanced photobiological production of H? in an aerobic, nitrogen-containing environment.

SUBMITTER: Masukawa H 

PROVIDER: S-EPMC2953041 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature