3HEN

Ferric Horse Heart Myoglobin; H64V/V67R Mutant

3HEN の概要

• エントリーDOI: 10.2210/pdb3hen/pdb
• 関連するPDBエントリー: 3HC9 3HDW 3HEO 3HEP
• 分子名称: Myoglobin, PROTOPORPHYRIN IX CONTAINING FE, PHOSPHATE ION, ... (4 entities in total)
• 機能のキーワード: ferric myoglobin, horse heart, h64v/v67r mutant, heme, iron, metal-binding, muscle protein, oxygen transport, transport
• 由来する生物種: Equus caballus (domestic horse, equine)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 17714.02

構造登録者

Yi, J.,Thomas, L.M.,Richter-Addo, G.B. (登録日: 2009-05-09, 公開日: 2009-12-29, 最終更新日: 2023-09-06)

主引用文献

Yi, J.,Heinecke, J.,Tan, H.,Ford, P.C.,Richter-Addo, G.B.
The distal pocket histidine residue in horse heart myoglobin directs the o-binding mode of nitrite to the heme iron.
J.Am.Chem.Soc., 131:18119-18128, 2009

PubMed Abstract: 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.

PubMed: 19924902
DOI: 10.1021/ja904726q

実験手法

X-RAY DIFFRACTION (1.9 Å)