Strong modulation of nitrite reductase activity of cytoglobin by disulfide bond oxidation: Implications for nitric oxide homeostasis

Abstract

Globin-mediated nitric oxide (NO) dioxygenase and nitrite reductase activities have been proposed to serve protective functions within the cell by scavenging or generating NO respectively. Cytoglobin has rapid NO dioxygenase activity, similar to other globins, however, the apparent rates of nitrite reductase activity have been reported as slow or negligible. Here we report that the activity of cytoglobin nitrite reductase activity is strongly dependent on the oxidation state of the two surface-exposed cysteine residues. The formation of an intramolecular disulfide bond between cysteines C38 and C83 enhances the nitrite reductase activity by 50-fold over that of the monomer with free sulfhydryl or 140-fold over that of the dimer with intermolecular disulfide bonds. The NO dioxygenase reactivity of cytoglobin is very rapid with or without disulfide bond, however, binding of the distal histidine following dissociation of the nitrate are affected by the presence or absence of the disulfide bond. The nitrite reductase activity reported here for the monomer with intramolecular disulfide is much higher than of those previously reported for other mammalian globins, suggesting a plausible role for this biochemistry in controlling NO homeostasis the cell under oxidative and ischemic conditions.

Molecular Dynamics Simulation and Kinetic Study of Fluoride Binding to V21C/V66C Myoglobin with a Cytoglobin-like Disulfide Bond

“…Note that multiple water molecules were also observed in the X-ray structure of Mb with a modified heme Moreover, as a consequence of structural rearrangement, the spatial orientation of heme distal His64 is different in the two protein complexes (indicated by a circle line in Figure 3), although the heme axial fluoride ions, as well as the distal water molecules, overlapped very well. This observation suggests that the formation of an intramolecular disulfide bond can regulate the conformation of heme distal histidine, thereby fine-tuning the ligand binding property and protein reactivity, as those observed for native Cgb with a bis-His heme coordination [27][28][29][30].…”

“…For example, manganese peroxidase (MnP) contains five disulfide bonds, and engineering an additional disulfide bond can further increase its tolerance for heat inactivation [23,24]. Disulfide bond has also been shown to regulate the binding of ligands in native heme proteins, as observed for neuroglobin (Ngb) [25,26] and cytoglobin (Cgb) [27][28][29][30]. Note that both Ngb and Cgb are relatively newly discovered globins, with a bis-His coordinated heme and an intramolecular disulfide bond [26,27].…”

Peroxidase Activity of Human Hemoproteins: Keeping the Fire under Control

“…Mammalian globins have a typical structure: a protein consists of six to eight helical chains arranged in a three-on-three helix ‘‘sandwich’’, forming the hydrophobic pocket of the active center containing heme [ 25 ]. All members of the globin family possess NO dioxygenase activity and participate in NO metabolism [ 143 , 144 , 145 ].…”

Nitrite Improves Heart Regeneration in Zebrafish

“…The decrease in oxygen tension switches Mb from acting as an NO scavenger in normoxia to a nitrite reductase in hypoxia (22,54,61). In addition to Mb, hemoglobin (Hb), neuroglobin, and cytoglobin have all been reported to reduce nitrite to NO in various mammalian tissues during hypoxia with significant physiological effects, such as vasodilation and cardioprotection through modulation of mitochondrial respiration (7,24,26,40,55,68).…”