Dataset Information

Influence of distal residue B10 on CO dynamics in myoglobin and neuroglobin.

ABSTRACT: For many years, myoglobin has served as a paradigm for structure-function studies in proteins. Ligand binding and migration within myoglobin has been studied in great detail by crystallography and spectroscopy, showing that gaseous ligands such as O(2), CO, and NO not only bind to the heme iron but may also reside transiently in three internal ligand docking sites, the primary docking site B and secondary sites C and D. These sites affect ligand association and dissociation in specific ways. Neuroglobin is another vertebrate heme protein that also binds small ligands. Ligand migration pathways in neuroglobin have not yet been elucidated. Here, we have used Fourier transform infrared temperature derivative spectroscopy at cryogenic temperatures to compare the influence of the side chain volume of amino acid residue B10 on ligand migration to and rebinding from docking sites in myoglobin and neuroglobin.

SUBMITTER: Nienhaus K

PROVIDER: S-EPMC2565765 | biostudies-other | 2007 Dec

REPOSITORIES: biostudies-other

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Influence of distal residue B10 on CO dynamics in myoglobin and neuroglobin.

Nienhaus Karin K Nienhaus G Ulrich GU

Journal of biological physics 20071201 5-6

For many years, myoglobin has served as a paradigm for structure-function studies in proteins. Ligand binding and migration within myoglobin has been studied in great detail by crystallography and spectroscopy, showing that gaseous ligands such as O(2), CO, and NO not only bind to the heme iron but may also reside transiently in three internal ligand docking sites, the primary docking site B and secondary sites C and D. These sites affect ligand association and dissociation in specific ways. Neu ...[more]

PMID: 19669524

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Project description:It is now well-established that mammalian heme proteins are reactive with various nitrogen oxide species and that these reactions may play significant roles in mammalian physiology. For example, the ferrous heme protein myoglobin (Mb) has been shown to reduce nitrite (NO(2)(-)) to nitric oxide (NO) under hypoxic conditions. We demonstrate here that the distal pocket histidine residue (His64) of horse heart metMb(III) (i.e., ferric Mb(III)) has marked effects on the mode of nitrite ion coordination to the iron center. X-ray crystal structures were determined for the mutant proteins metMb(III) H64V (2.0 A resolution) and its nitrite ion adduct metMb(III) H64V-nitrite (1.95 A resolution), and metMb(III) H64V/V67R (1.9 A resolution) and its nitrite ion adduct metMb(III) H64V/V67R-nitrite (2.0 A resolution). These are compared to the known structures of wild-type (wt) hh metMb(III) and its nitrite ion adduct hh metMb(III)-nitrite, which binds NO(2)(-) via an O-atom in a trans-FeONO configuration. Unlike wt metMb(III), no axial H(2)O is evident in either of the metMb(III) mutant structures. In the ferric H64V-nitrite structure, replacement of the distal His residue with Val alters the binding mode of nitrite from the nitrito (O-binding) form in the wild-type protein to a weakly bound nitro (N-binding) form. Reintroducing a H-bonding residue in the H64V/V67R double mutant restores the O-binding mode of nitrite. We have also examined the effects of these mutations on reactivities of the metMb(III)s with cysteine as a reducing agent and of the (ferrous) Mb(II)s with nitrite ion under anaerobic conditions. The Mb(II)s were generated by reduction of the Mb(III) precursors in a second-order reaction with cysteine, the rate constants for this step following the order H64V/V67R > H64V >> wt. The rate constants for the oxidation of the Mb(II)s by nitrite (giving NO as the other product) follow the order wt > H64V/V67R >> H64V and suggest a significant role of the distal pocket H-bonding residue in nitrite reduction.

Dataset Information

Influence of distal residue B10 on CO dynamics in myoglobin and neuroglobin.

Publications

Influence of distal residue B10 on CO dynamics in myoglobin and neuroglobin.

Similar Datasets

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