3sdh
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(New page: 200px<br /> <applet load="3sdh" size="450" color="white" frame="true" align="right" spinBox="true" caption="3sdh, resolution 1.4Å" /> '''HIGH RESOLUTION CRYS...)
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Revision as of 11:28, 8 November 2007
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HIGH RESOLUTION CRYSTALLOGRAPHIC ANALYSIS OF A COOPERATIVE DIMERIC HEMOGLOBIN
Overview
High-resolution crystal structures of the co-operative dimeric hemoglobin, from the blood clam Scapharca inaequivalvis have been determined in the, unliganded (deoxy) and carbon monoxide (CO) liganded states. The deoxy, structure has been refined at 1.6 A resolution to an R-factor of 0.158 and, the CO structure has been refined at 1.4 A resolution to an R-factor of, 0.159. These structures reveal details of the structural transitions, involved in co-operative ligand binding that involve only a minor rotation, of subunits but very striking tertiary changes at the interface. A small, number of residues in the F-helix appear to mediate co-operativity in this, simple hemoglobin. The oxygen affinity of each subunit appears to be, largely dictated by the disposition of phenylalanine 97, whose side-chain, packs in the heme pocket in the deoxy state but is extruded towards the, interface in the CO-liganded structure. Direct involvement of the, ligand-binding heme group is a novel feature of the subunit interface and, appears important for intersubunit communication. Ligation alters the, conformation of the heme propionate groups along with two interacting, residues from the symmetry-related subunit. These two residues, lysine 96, and asparagine 100, link the heme of one subunit with the F-helix of the, second subunit in such a way as to influence the ligand affinity of that, subunit. The interface is highly hydrated by well-ordered water molecules, that are likely to be important in the stabilization of the two, structures.
About this Structure
3SDH is a Single protein structure of sequence from Scapharca inaequivalvis with HEM and CMO as ligands. This structure superseeds the now removed PDB entry 1SDH. Full crystallographic information is available from OCA.
Reference
High-resolution crystallographic analysis of a co-operative dimeric hemoglobin., Royer WE Jr, J Mol Biol. 1994 Jan 14;235(2):657-81. PMID:8289287
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