HupW protease specifically required for processing of the catalytic subunit of the uptake hydrogenase in the cyanobacterium Nostoc sp. strain PCC 7120.

The maturation process of [NiFe] hydrogenases includes a proteolytic cleavage of the large subunit. We constructed a mutant of Nostoc strain PCC 7120 in which hupW, encoding a putative hydrogenase-specific protease, is inactivated. Our results indicate that the protein product of hupW selectively cleaves the uptake hydrogenase in this cyanobacterium.

A HupS-GFP fusion protein demonstrates a heterocyst-specific localization of the uptake hydrogenase in Nostoc punctiforme.

All diazotrophic filamentous cyanobacteria contain an uptake hydrogenase that is involved in the reoxidation of H(2) produced during N(2) -fixation. In Nostoc punctiforme ATCC 29133, N(2) -fixation takes place in the microaerobic heterocysts, catalysed by a nitrogenase. Although the function of the uptake hydrogenase may be closely connected to that of nitrogenase, the localization in cyanobacteria has been under debate.

CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120.

The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth conditions, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit.

Diversity and transcription of proteases involved in the maturation of hydrogenases in Nostoc punctiforme ATCC 29133 and Nostoc sp. strain PCC 7120.

Background: The last step in the maturation process of the large subunit of [NiFe]-hydrogenases is a proteolytic cleavage of the C-terminal by a hydrogenase specific protease. Contrary to other accessory proteins these hydrogenase proteases are believed to be specific whereby one type of hydrogenases specific protease only cleaves one type of hydrogenase. In cyanobacteria this is achieved by the gene product of either hupW or hoxW, specific for the uptake or the bidirectional hydrogenase respectively.