The nirQ gene, which is required for denitrification of Pseudomonas aeruginosa, can activate the RubisCO from Pseudomonas hydrogenothermophila.

Two putative ATP-binding proteins encoded in the gene cluster for the Calvin cycle of Pseudomonas hydrogenothermophila (cbbQ) and for the denitrification of Pseudomonas aeruginosa (nirQ) have been found to be similar. The cbbQ gene has been shown to activate the RubisCO from P. hydrogenothermophila in E. coli. The nirQ was functionally substituted for cbbQ. The nirQ gene restored the anaerobic growth and the NOR activity of the nirQOP mutant of P. aeruginosa, while the cbbQ gene did not.