1NWI

Crystal structure of CO-HbI transformed to an unligated state

1NWI の概要

• エントリーDOI: 10.2210/pdb1nwi/pdb
• 関連するPDBエントリー: 1NWN 3SDH 4SDH
• 分子名称: globin I, PROTOPORPHYRIN IX CONTAINING FE (3 entities in total)
• 機能のキーワード: invertebrate, hemoglobin, allostery, cooperativity, oxygen-binding, oxygen transport, heme protein, oxygen storage-transport complex, oxygen storage/transport
• 由来する生物種: Scapharca inaequivalvis (ark clam)
• 細胞内の位置: Cytoplasm: P02213
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 66331.22

構造登録者

Knapp, J.E.,Royer JR., W.E. (登録日: 2003-02-06, 公開日: 2003-08-26, 最終更新日: 2023-08-16)

主引用文献

Knapp, J.E.,Royer Jr., W.E.
Ligand-linked structural transitions in crystals of a cooperative dimeric hemoglobin.
Biochemistry, 42:4640-4647, 2003

PubMed Abstract: Cooperative ligand binding in the dimeric hemoglobin (HbI) from the blood clam Scapharca inaequivalvis is mediated primarily by tertiary structural changes, but with a small quaternary rearrangement (approximately 3 degrees), based on analysis of distinct crystal forms for ligated and unligated molecules. We report here ligand transition structures in both crystal forms. Binding CO to unligated HbI crystals results in a structure that approaches, but does not attain, the full allosteric transition. In contrast, removing CO from the HbI-CO crystals results in a structure that possesses all the key low affinity attributes previously identified from analysis of HbI crystals grown in the unligated state. Subsequent binding of CO shows the reversibility of this process. The observed structural changes include the quaternary rearrangement even under the constraints of lattice interactions, demonstrating that subunit rotation is an integral component of the ligand-linked structural transition in HbI. Analysis of both crystal forms, along with data from HbI mutants, suggests that the quaternary structural change is linked to the movement of the heme group, supporting a hypothesis that the heme movement is the central event that triggers cooperative ligand binding in this hemoglobin dimer. These results show both the effects of a crystal lattice in limiting quaternary structural transitions and provide the first example of complete allosteric transitions within another crystal lattice.

PubMed: 12705827
DOI: 10.1021/bi027136p

実験手法

X-RAY DIFFRACTION (2.5 Å)