In silico and wet-lab study revealed cadmium is the potent inhibitor of HupL in Anabaena sp. PC C 7120.

The hupL of Anabaena sp. PCC 7120 encodes the large subunit of uptake hydrogenase found in all diazotrophic cyanobacteria and boosts up the nitrogen-fixing potential by catalyzing the removal of the molecular hydrogen produced as a by-product of dinitrogen fixation. Bioinformatics analysis revealed that HupL from Anabaena sp. PCC7120 is a 60.2 kDa, thermostable, glycine-rich protein having highest structural similarity with NiFeSe hydrogenase of Desulfomicrobium baculatumis. Toxicity of selected abiotic stresses like arsenic, cadmium, copper, and salt with HupL was further reconciled by wet-lab approaches like qRT-PCR, hydrogenase and nitrogenase activity assay as hydrogenases unintendedly affect the nitrogenase activity in Anabaena. Down-regulated transcript along with highly inhibited hydrogenase and nitrogenase activities under cadmium stress revealed that cadmium is a potent inhibitor of hydrogenases in Anabaena which indirectly affects its nitrogen-fixing capabilities