2hz1
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The x-ray crystal structure of ferrous Synechocystis hemoglobin with a covalent linkage
OverviewOverview
Synechocystis hemoglobin contains an unprecedented covalent bond between a, nonaxial histidine side chain (H117) and the heme 2-vinyl. This bond has, been previously shown to stabilize the ferric protein against, denaturation, and also to affect the kinetics of cyanide association., However, it is unclear why Synechocystis hemoglobin would require the, additional degree of stabilization accompanying the His117-heme 2-vinyl, bond because it also displays endogenous bis-histidyl axial heme, coordination, which should greatly assist heme retention. Furthermore, the, mechanism by which the His117-heme 2-vinyl bond affects ligand binding has, not been reported, nor has any investigation of the role of this bond on, the structure and function of the protein in the ferrous oxidation state., Here we report an investigation of the role of the Synechocystis, hemoglobin His117-heme 2-vinyl bond on structure, heme coordination, exogenous ligand binding, and stability in both the ferrous and ferric, oxidation states. Our results reveal that hexacoordinate Synechocystis, hemoglobin lacking this bond is less stable in the ferrous oxidation state, than the ferric, which is surprising in light of our understanding of, pentacoordinate Hb stability, in which the ferric protein is always less, stable. It is also demonstrated that removal of the His117-heme 2-vinyl, bond increases the affinity constant for intramolecular histidine, coordination in the ferric oxidation state, thus presenting greater, competition for the ligand binding site and lowering the observed rate and, affinity constants for exogenous ligands.
About this StructureAbout this Structure
2HZ1 is a Single protein structure of sequence from Synechocystis sp. with CD, SO3, HEM and SO2 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Covalent heme attachment in Synechocystis hemoglobin is required to prevent ferrous heme dissociation., Hoy JA, Smagghe BJ, Halder P, Hargrove MS, Protein Sci. 2007 Feb;16(2):250-60. PMID:17242429
Page seeded by OCA on Thu Nov 8 13:32:23 2007