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| '''Crystal Structure of Scapharca inaequivalvis HbI, I114F Mutant Ligated to Carbon Monoxide.'''
| | ===Crystal Structure of Scapharca inaequivalvis HbI, I114F Mutant Ligated to Carbon Monoxide.=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11732898}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11732898 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11732898}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Invertebrate hemoglobin]] | | [[Category: Invertebrate hemoglobin]] |
| [[Category: Oxygen-binding protein]] | | [[Category: Oxygen-binding protein]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 22:00:57 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:33:18 2008'' |