1shr
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Crystal structure of ferrocyanide bound human hemoglobin A2 at 1.88A resolution
OverviewOverview
Hemoglobin A(2) (alpha(2)delta(2)) is an important hemoglobin variant, which is a minor component (2-3%) in the circulating red blood cells, and, its elevated concentration in beta-thalassemia is a useful clinical, diagnostic. In beta-thalassemia major, where there is beta-chain, production failure, HbA(2) acts as the predominant oxygen deliverer., HbA(2) has two more important features. (1) It is more resistant to, thermal denaturation than HbA, and (2) it inhibits the polymerization of, deoxy sickle hemoglobin (HbS). Hemoglobin E (E26K(beta)), formed as a, result of the splice site mutation on exon 1 of the beta-globin gene, is, another important hemoglobin variant which is known to be unstable at high, temperatures. Both heterozygous HbE (HbAE) and homozygous HbE (HbEE) are, benign disorders, but when HbE combines with beta-thalassemia, it causes, E/beta-thalassemia which has severe clinical consequences. In this paper, we present the crystal structures of HbA(2) and HbE at 2.20 and 1.74 A, resolution, respectively, in their R2 states, which have been used here to, provide the probable explanations of the thermal stability and instability, of HbA(2) and HbE. Using the coordinates of R2 state HbA(2), we modeled, the structure of T state HbA(2) which allowed us to address the structural, basis of the antisickling property of HbA(2). Using the coordinates of the, delta-chain of HbA(2) (R2 state), we also modeled the structure of, hemoglobin homotetramer delta(4) that occurs in the case of rare HbH, disease. From the differences in intersubunit contacts among beta(4), gamma(4), and delta(4), we formed a hypothesis regarding the possible, tetramerization pathway of delta(4). The crystal structure of a, ferrocyanide-bound HbA(2) at 1.88 A resolution is also presented here, which throws light on the location and the mode of binding of ferrocyanide, anion with hemoglobin, predominantly using the residues involved in DPG, binding. The pH dependence of ferrocyanide binding with hemoglobin has, also been investigated.
DiseaseDisease
Known diseases associated with this structure: Erythremias, alpha- OMIM:[141800], Erythrocytosis OMIM:[141850], Heinz body anemia OMIM:[141850], Heinz body anemias, alpha- OMIM:[141800], Hemoglobin H disease OMIM:[141850], Hypochromic microcytic anemia OMIM:[141850], Methemoglobinemias, alpha- OMIM:[141800], Thalassemia due to Hb Lepore OMIM:[142000], Thalassemia, alpha- OMIM:[141850], Thalassemia, delta- OMIM:[142000], Thalassemias, alpha- OMIM:[141800]
About this StructureAbout this Structure
1SHR is a Protein complex structure of sequences from Homo sapiens with CYN, FE and HEM as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of HbA2 and HbE and modeling of hemoglobin delta 4: interpretation of the thermal stability and the antisickling effect of HbA2 and identification of the ferrocyanide binding site in Hb., Sen U, Dasgupta J, Choudhury D, Datta P, Chakrabarti A, Chakrabarty SB, Chakrabarty A, Dattagupta JK, Biochemistry. 2004 Oct 5;43(39):12477-88. PMID:15449937
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