1x9f
From Proteopedia
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Hemoglobin Dodecamer from Lumbricus Erythrocruorin
Overview
Erythrocruorins are highly cooperative giant extracellular respiratory, complexes found in annelids, where they serve the same function as red, blood cells. Our previous 5.5A resolution crystal structure of Lumbricus, terrestris erythrocruorin revealed a hierarchical organization of 144, oxygen-binding hemoglobin chains that are assembled into 12 dodecamers, arranged at the periphery of the complex around a central scaffold formed, by 36 non-hemoglobin subunits. We present here the 2.6A resolution crystal, structure of the Lumbricus hemoglobin dodecameric subassembly, which, provides the first atomic models of the erythrocruorin allosteric core., The hemoglobin dodecamer has a molecular 3-fold axis of symmetry that, relates three heterotetramers, each of which is composed of two tightly, associated heterodimers. The structure reveals details of the interfaces, including key side-chain interactions likely to contribute to, ligand-linked allosteric transitions, and shows the crowded nature of the, ligand-binding pockets. Comparison of the Lumbricus dimeric assemblies, with similar ones from mollusks and echinoderms suggests plausible, pH-dependent quaternary transitions that may occur in response to proton, binding and ligand release. Thus, these results provide the first step, towards elucidating the structural basis for the strong allosteric, properties of Lumbricus erythrocruorin.
About this Structure
1X9F is a Protein complex structure of sequences from Lumbricus terrestris with PO4, HEM and CMO as ligands. Full crystallographic information is available from OCA.
Reference
Crystal structure of the hemoglobin dodecamer from Lumbricus erythrocruorin: allosteric core of giant annelid respiratory complexes., Strand K, Knapp JE, Bhyravbhatla B, Royer WE Jr, J Mol Biol. 2004 Nov 12;344(1):119-34. PMID:15504406
Page seeded by OCA on Thu Nov 8 13:21:10 2007
