1nwi | pdb_00001nwi

Crystal structure of CO-HbI transformed to an unligated state

spinqualitylabelsall models 1nwi, resolution 2.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1nwi is a 4 chain structure with sequence from Anadara inaequivalvis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.5Å Ligands: HEM Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function GLB1_ANAIN Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 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. Ligand-linked structural transitions in crystals of a cooperative dimeric hemoglobin.,Knapp JE, Royer WE Jr Biochemistry. 2003 Apr 29;42(16):4640-7. PMID:12705827 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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