1YMA

STRUCTURAL CHARACTERIZATION OF HEME LIGATION IN THE HIS64-->TYR VARIANT OF MYOGLOBIN

1YMA の概要

• エントリーDOI: 10.2210/pdb1yma/pdb
• 分子名称: MYOGLOBIN, SULFATE ION, PROTOPORPHYRIN IX CONTAINING FE, ... (4 entities in total)
• 機能のキーワード: oxygen transport
• 由来する生物種: Equus caballus (horse)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 17721.09

構造登録者

Maurus, R.,Brayer, G.D. (登録日: 1993-09-27, 公開日: 1994-01-31, 最終更新日: 2024-02-14)

主引用文献

Maurus, R.,Bogumil, R.,Luo, Y.,Tang, H.L.,Smith, M.,Mauk, A.G.,Brayer, G.D.
Structural characterization of heme ligation in the His64-->Tyr variant of myoglobin.
J.Biol.Chem., 269:12606-12610, 1994

PubMed Abstract: A site-specific mutant of horse heart myoglobin has been prepared in which the distal heme pocket residue, His64, is replaced by tyrosine. The structure of this myoglobin variant has been determined to 2.0-A resolution using x-ray diffraction techniques and refined to a final crystallographic R-factor of 16.9%. The polypeptide backbone conformation of the His64-->Tyr variant of myoglobin is very similar to that of the wild-type protein. However, in the variant the water normally found coordinated to the heme iron atom and hydrogen-bonded to His64 has been displaced by the hydroxyl oxygen of the Tyr64 side chain. The tyrosine oxygen atom is directly coordinated to the heme iron atom with a bond length of 2.18 A. Distortion of heme planarity and changes in the packing of the Leu29 and Leu104 side chains are related to this mutation. The ligand environment of the ferric iron has been studied by electron paramagnetic resonance (EPR) spectroscopy using crystalline material and protein in solution. The protein in solution exhibits a rhombically split ferric high spin EPR spectrum with g values of 6.64, 5.34, and 1.98. The EPR spectrum of the crystalline sample consists of two different ferric high spin signals. The main signal is similar to the signal observed in solution and is assigned to His93-Fe(III)-Tyr64 coordination. The relatively high rhombicity of this signal can be explained as arising from distortions of the heme plane seen in the crystal structure. The second, more axial high spin signal found in the crystalline state can be tentatively assigned to another form of iron ligation with a different iron-tyrosine bond length and a less distorted heme plane.

PubMed: 8175669

実験手法

X-RAY DIFFRACTION (2 Å)