1jzk
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Crystal Structure of Scapharca inaequivalvis HbI, I114F mutant (deoxy)
OverviewOverview
Cooperative ligand binding in the dimeric hemoglobin from the blood clam, Scapharca inaequivalvis results primarily from tertiary, rather than, quaternary, structural changes. Ligand binding is coupled with, conformational changes of key residues, including Phe 97, which is, extruded from the proximal heme pocket, and the heme group, which moves, deeper into the heme pocket. We have tested the role of the heme movement, in cooperative function by mutating Ile 114, at the base of the heme, pocket. Replacement of this residue with a Met did not disturb the, hemoglobin structure or significantly alter equilibrium ligand binding, properties. In contrast, substitution with a Phe at position 114 inhibits, the ligand-linked movement of the heme group, and substantially reduces, oxygen affinity and cooperativity. As the extent of heme movement to the, normal position of the ligated state is diminished, Phe 97 is inhibited, from its movement into the interface upon ligand binding. These results, indicate a tight coupling between these two key cooperative transitions, and suggest that the heme movement may be an obligatory trigger for, expulsion of Phe 97 from the heme pocket.
About this StructureAbout this Structure
1JZK is a Single protein structure of sequence from Scapharca inaequivalvis with HEM as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Restricting the ligand-linked heme movement in Scapharca dimeric hemoglobin reveals tight coupling between distal and proximal contributions to cooperativity., Knapp JE, Gibson QH, Cushing L, Royer WE Jr, Biochemistry. 2001 Dec 11;40(49):14795-805. PMID:11732898
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