2z8a | pdb_00002z8a
Ligand Migration and Binding in The Dimeric Hemoglobin of Scapharca Inaequivalvis: I25W with CO Bound to HEME and in the Presence of 3 Atoms of XE
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Overview
Using Fourier transform infrared (FTIR) spectroscopy combined with, temperature derivative spectroscopy (TDS) at cryogenic temperatures, we, have studied CO binding to the heme and CO migration among cavities in the, interior of the dimeric hemoglobin of Scapharca inaequivalvis (HbI) after, photodissociation. By combining these studies with X-ray crystallography, three transient ligand docking sites were identified: a primary docking, site B in close vicinity to the heme iron, and two secondary docking sites, C and D corresponding to the Xe4 and Xe2 cavities of myoglobin. To assess, the relevance of these findings for physiological binding, we also, performed flash photolysis experiments on HbICO at room temperature and, equilibrium binding studies with dioxygen. Our results show that the Xe4, and Xe2 cavities serve as transient docking sites for unbound ligands in, the protein, but not as way stations on the entry/exit pathway. For HbI, the so-called histidine gate mechanism proposed for other globins appears, as a plausible entry/exit route as well.
About this Structure
2Z8A is a Single protein structure of sequence from Scapharca inaequivalvis with PO4, HEM, CMO and XE as ligands. Full crystallographic information is available from OCA.
Reference
Ligand Migration and Binding in the Dimeric Hemoglobin of Scapharca inaequivalvis(,)., Nienhaus K, Knapp JE, Palladino P, Royer WE Jr, Nienhaus GU, Biochemistry. 2007 Nov 15;. PMID:18001141
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