TY - JOUR
T1 - Nitrosyl Myoglobins and Their Nitrite Precursors
T2 - Crystal Structural and Quantum Mechanics and Molecular Mechanics Theoretical Investigations of Preferred Fe -NO Ligand Orientations in Myoglobin Distal Pockets
AU - Wang, Bing
AU - Shi, Yelu
AU - Tejero, Jesús
AU - Powell, Samantha M.
AU - Thomas, Leonard M.
AU - Gladwin, Mark T.
AU - Shiva, Sruti
AU - Zhang, Yong
AU - Richter-Addo, George B.
N1 - Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/8/14
Y1 - 2018/8/14
N2 - The globular dioxygen binding heme protein myoglobin (Mb) is present in several species. Its interactions with the simple nitrogen oxides, namely, nitric oxide (NO) and nitrite, have been known for decades, but the physiological relevance has only recently become more fully appreciated. We previously reported the O-nitrito mode of binding of nitrite to ferric horse heart wild-type (wt) MbIII and human hemoglobin. We have expanded on this work and report the interactions of nitrite with wt sperm whale (sw) MbIII and its H64A, H64Q, and V68A/I107Y mutants whose dissociation constants increase in the following order: H64Q < wt < V68A/I107Y < H64A. We also report their X-ray crystal structures that reveal the O-nitrito mode of binding of nitrite to these derivatives. The MbII-mediated reductions of nitrite to NO and structural data for the wt and mutant MbII-NOs are described. We show that their FeNO orientations vary with distal pocket identity, with the FeNO moieties pointing toward the hydrophobic interiors when the His64 residue is present but toward the hydrophilic exterior when this His64 residue is absent in this set of mutants. This correlates with the nature of H-bonding to the bound NO ligand (nitrosyl O vs N atom). Quantum mechanics and hybrid quantum mechanics and molecular mechanics calculations help elucidate the origin of the experimentally preferred NO orientations. In a few cases, the calculations reproduce the experimentally observed orientations only when the whole protein is taken into consideration.
AB - The globular dioxygen binding heme protein myoglobin (Mb) is present in several species. Its interactions with the simple nitrogen oxides, namely, nitric oxide (NO) and nitrite, have been known for decades, but the physiological relevance has only recently become more fully appreciated. We previously reported the O-nitrito mode of binding of nitrite to ferric horse heart wild-type (wt) MbIII and human hemoglobin. We have expanded on this work and report the interactions of nitrite with wt sperm whale (sw) MbIII and its H64A, H64Q, and V68A/I107Y mutants whose dissociation constants increase in the following order: H64Q < wt < V68A/I107Y < H64A. We also report their X-ray crystal structures that reveal the O-nitrito mode of binding of nitrite to these derivatives. The MbII-mediated reductions of nitrite to NO and structural data for the wt and mutant MbII-NOs are described. We show that their FeNO orientations vary with distal pocket identity, with the FeNO moieties pointing toward the hydrophobic interiors when the His64 residue is present but toward the hydrophilic exterior when this His64 residue is absent in this set of mutants. This correlates with the nature of H-bonding to the bound NO ligand (nitrosyl O vs N atom). Quantum mechanics and hybrid quantum mechanics and molecular mechanics calculations help elucidate the origin of the experimentally preferred NO orientations. In a few cases, the calculations reproduce the experimentally observed orientations only when the whole protein is taken into consideration.
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U2 - 10.1021/acs.biochem.8b00542
DO - 10.1021/acs.biochem.8b00542
M3 - Article
C2 - 29999305
AN - SCOPUS:85050033092
SN - 0006-2960
VL - 57
SP - 4788
EP - 4802
JO - Biochemistry
JF - Biochemistry
IS - 32
ER -