FeNO Structure in Distal Pocket Mutants of Myoglobin Based on Resonance Raman Spectroscopy

Coyle, Christine M.; Vogel, Kathleen M.; Rush, Thomas S.; Kozłowski, Pawel M.; Williams, R. D.; Spiro, Thomas G.; Dou, Yi; Ikeda‐Saito, Masao; Olson, John S.; Zgierski, Marek Z.

doi:10.1021/bi026395b

Cited by 80 publications

(125 citation statements)

References 47 publications

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“…In ferric horse MbNO, an NO stretching band is found at 1927 cm Ϫ1 in the wild-type form and at 1904 cm Ϫ1 in the apolar mutant H64L (43). This observation shows that heme-bound NO has a similar sensitivity to its local environment as does CO (44). By analogy, we suggest that the two conformations of NP4 also differ in the polarity of the distal pocket, with the low pH A 1908 having a more hydrophobic distal pocket.…”

Section: Infrared Stretching Bands Of Heme-bound Ligands-mentioning

confidence: 64%

Structural Dynamics Controls Nitric Oxide Affinity in Nitrophorin 4

Nienhaus

Maes

Weichsel

et al. 2004

Journal of Biological Chemistry

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Nitrophorin 4 (NP4) is one of seven nitric oxide (NO) transporting proteins in the blood-sucking insect Rhodnius prolixus. In its physiological function, NO binds to a ferric iron centered in a highly ruffled heme plane. Carbon monoxide (CO) also binds after reduction of the heme iron. Here we have used Fourier transform infrared spectroscopy at cryogenic temperatures to study CO and NO binding and migration in NP4, complemented by x-ray cryo-crystallography on xenon-containing NP4 crystals to identify cavities that may serve as ligand docking sites. Multiple infrared stretching bands of the heme-bound ligands indicate different active site conformations with varying degrees of hydrophobicity. Narrow infrared stretching bands are observed for photodissociated CO and NO; temperature-derivative spectroscopy shows that these bands are associated with ligand docking sites close to the extremely reactive heme iron. No rebinding from distinct secondary sites was detected, although two xenon binding cavities were observed in the x-ray structure. Photolysis studies at ϳ200 K show efficient NO photoproduct formation in the more hydrophilic, open NP4 conformation. This result suggests that ligand escape is facilitated in this conformation, and blockage of the active site by water hinders immediate reassociation of NO to the ferric iron. In the closed, low-pH conformation, ligand escape from the active site of NP4 is prevented by an extremely reactive heme iron and the absence of secondary ligand docking sites. Nitrophorins (NPs)1 are proteins that transport nitric oxide (NO) from the salivary glands of blood-sucking insects to their victims, resulting in vasodilation and reduced blood coagulation (1-4). Seven nitrophorins (NP1-7) have been identified from Rhodnius prolixus (4 -6), all of which share the lipocalin fold (7) consisting of a ␤-barrel with a highly nonplanar, ruffled heme inserted into one end of the barrel and attached to the protein through a proximal histidine (8). Of the seven Rhodnius nitrophorins, NP4 has been particularly well characterized (10 -13).2 Like all other NPs, NP4 requires a ferric heme to function as an NO-binding protein. Reduction of the heme iron will cause nearly irreversible binding of NO. In the absence of NO, NP4 has a spacious distal pocket that allows easy solvent access (12). Upon NO binding, two loops, the A-B loop (residues 31-37) and the G-H loop (residues 125-132) pack tightly around the NO ligand and form a hydrophobic trap (13). The trapping mechanism utilizes the pH sensitivity of the protein conformation. At pH 5, the approximate pH of the insect saliva, the "closed" conformation is stabilized for the NO complex, whereas at pH 7, the approximate pH of the victim's tissue, the closed conformation is destabilized (2, 14).The kinetics of NO binding and release by NP4 are multiphasic (2, 14), implying static or dynamic active site heterogeneity, which was, however, not apparent in the ultra-high resolution x-ray structure of NP4NO at pH 5.6. In contrast to x-ray diffraction, in...

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Section: Infrared Stretching Bands Of Heme-bound Ligands-mentioning

confidence: 64%

Structural Dynamics Controls Nitric Oxide Affinity in Nitrophorin 4

Nienhaus

Maes

Weichsel

et al. 2004

Journal of Biological Chemistry

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“…However, even with those obtained at high resolution, there is a significant range of FeNO conformations that suggest a role of distal residues in influencing FeNO geometry through a combination of factors including steric and electrostatic effects. This has been illustrated very well for Mb II NO [93][94][95], and related studies are ongoing for heme proteins in general, as distal and proximal effects are likely determinants of ligand discrimination and selectivity in heme-based sensor proteins. The role of cavity size in influencing FeNO bond angles has been demonstrated very well in the non-heme [(L)Fe(NO)] À anions (L = derivative of tris(N-R-carbamoylmethyl)amine), where the angle is 178.2(5)°when R = isopropyl, and 160.3(2)°when R = 3,5-dimethylphenyl [96].…”

Section: The Mb II No Structuresmentioning

confidence: 74%

Crystal structures of the nitrite and nitric oxide complexes of horse heart myoglobin

Copeland

Soares

West

et al. 2006

Journal of Inorganic Biochemistry

106

135

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“…From these observations, we concluded that OS-II has the heme iron directly coordinated by the N atom of butyraldoxime. Intriguingly, the 857-cm -1 vibrational frequency is much higher than the Fe-N single bond stretching frequency (500-600 cm -1 ) observed for the NO adducts of hemoproteins (41,42). Previously, Wagner and Nakamoto (43,44) reported a similar high Fe-N stretching frequency (876 cm -1 ) in the RR spectra of the photolysis products of the tetraphenylporphyrin azide complex, for which the formation of a perferryliron-N triple bond [Fe(V)ϵN] was proposed.…”

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confidence: 74%