Identification of a stable complex between a [NiFe]-hydrogenase catalytic subunit and its maturation protease

Salmonella enterica serovar Typhimurium has the ability to use molecular hydrogen as a respiratory electron donor. This is facilitated by three [NiFe]-hydrogenases termed Hyd-1, Hyd-2, and Hyd-5. Hyd-1 and Hyd-5 are homologous oxygen-tolerant [NiFe]-hydrogenases. A critical step in the biosynthesis of a [NiFe]-hydrogenase is the proteolytic processing of the catalytic subunit. In this work, the role of the maturation protease encoded within the Hyd-5 operon, HydD, was found to be partially complemented by the maturation protease encoded in the Hyd-1 operon, HyaD. In addition, both maturation proteases were shown to form stable complexes, in vivo and in vitro, with the catalytic subunit of Hyd-5. The protein–protein interactions were not detectable in a strain that could not make the enzyme metallocofactor.