Publication Abstract from PubMed
Heme proteins are important entities for the metabolism of nitrite. Inspection of the structural features of the reported hemoproteinnitrite crystal structures reveals that, except for nitrophorin 4 (NP4), H-bonding to the nitrite ligand is accomplished via histidine or arginine residues. These H-bonds probably play an important role for the nitrite coordination and/or reactivities. In nitrophorins, which catalyze the nitrite disproportionation reaction, such a residue is missing. Here, we report on the L130R mutant of the NP isoprotein NP4 that provides the Arg130 residue as part of the flexible GH loop as a potential H-bonding residue in the distal heme pocket. Similar to the wild-type protein, nitrite remains N-bonded in the crystal structure of NP4(L130R). However, spectroscopic investigations show that, in solution, a second ligand-rotational orientation exists, which is in fast-exchange equilibrium with the normal, parallel ligand orientation. Moreover, the nitrite disproportionation is inhibited in NP4(L130R). Comparison with another, also less active mutant NP4(D30N) suggests that the displacement of H(2) O molecules from the heme cavity prevents the proton donation pathway through Asp30.
Insertion of an h-bonding residue into the distal pocket of the ferriheme protein nitrophorin 4: effect on nitriteiron coordination and nitrite disproportionation.,He C, Ogata H, Knipp M Chem Biodivers. 2012 Sep;9(9):1761-75. doi: 10.1002/cbdv.201100401. PMID:22976968[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
