1DSE

CYTOCHROME C PEROXIDASE H175G MUTANT, IMIDAZOLE COMPLEX, WITH PHOSPHATE BOUND, PH 6, 100K

1DSE の概要

• エントリーDOI: 10.2210/pdb1dse/pdb
• 関連するPDBエントリー: 1CCA 1DSE 1DSG 1DSO 1DSP
• 分子名称: CYTOCHROME C PEROXIDASE, PHOSPHATE ION, PROTOPORPHYRIN IX CONTAINING FE, ... (5 entities in total)
• 機能のキーワード: heme enzyme, peroxidase, cavity mutant, ligand binding, oxidoreductase
• 由来する生物種: Saccharomyces cerevisiae (baker's yeast)
• 細胞内の位置: Mitochondrion matrix: P00431
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 34025.50

構造登録者

Hirst, J.,Wilcox, S.K.,Williams, P.A.,McRee, D.E.,Goodin, D.B. (登録日: 2000-01-07, 公開日: 2001-03-07, 最終更新日: 2024-02-07)

主引用文献

Hirst, J.,Wilcox, S.K.,Williams, P.A.,Blankenship, J.,McRee, D.E.,Goodin, D.B.
Replacement of the axial histidine ligand with imidazole in cytochrome c peroxidase. 1. Effects on structure.
Biochemistry, 40:1265-1273, 2001

PubMed Abstract: Replacement of the axial histidine ligand with exogenous imidazole has been accomplished in a number of heme protein mutants, where it often serves to complement the functional properties of the protein. In this paper, we describe the effects of pH and buffer ion on the crystal structure of the H175G mutant of cytochrome c peroxidase, in which the histidine tether between the heme and the protein backbone is replaced by bound imidazole. The structures show that imidazole can occupy the proximal H175G cavity under a number of experimental conditions, but that the details of the interaction with the protein and the coordination to the heme are markedly dependent on conditions. Replacement of the tethered histidine ligand with imidazole permits the heme to shift slightly in its pocket, allowing it to adopt either a planar or distally domed conformation. H175G crystallized from both high phosphate and imidazole concentrations exists as a novel, 5-coordinate phosphate bound state, in which the proximal imidazole is dissociated and the distal phosphate is coordinated to the iron. To accommodate this bound phosphate, the side chains of His-52 and Asn-82 alter their positions and a significant conformational change in the surrounding protein backbone occurs. In the absence of phosphate, imidazole binds to the proximal H175G cavity in a pH-dependent fashion. At pH 7, imidazole is directly coordinated to the heme (d(Fe--Im) = 2.0 A) with a nearby distal water (d(Fe--HOH) = 2.4 A). This is similar to the structure of WT CCP except that the iron lies closer in the heme plane, and the hydrogen bond between imidazole and Asp-235 (d(Im--Asp) = 3.1 A) is longer than for WT CCP (d(His--Asp) = 2.9 A). As the pH is dropped to 5, imidazole dissociates from the heme (d(Fe--Im) = 2.9 A), but remains in the proximal cavity where it is strongly hydrogen bonded to Asp-235 (d(Im--Asp) = 2.8 A). In addition, the heme is significantly domed toward the distal pocket where it may coordinate a water molecule. Finally, the structure of H175G/Im, pH 6, at low temperature (100 K) is very similar to that at room temperature, except that the water above the distal heme face is not present. This study concludes that steric restrictions imposed by the covalently tethered histidine restrain the heme and its ligand coordination from distortions that would arise in the absence of the restricted tether. Coupled with the functional and spectroscopic properties described in the following paper in this issue, these structures help to illustrate how the delicate and critical interactions between protein, ligand, and metal modulate the function of heme enzymes.

PubMed: 11170452
DOI: 10.1021/bi002089r

実験手法

X-RAY DIFFRACTION (2 Å)