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From Proteopedia
Crystal Structures of Unliganded and Half-Liganded Human Hemoglobin Derivatives Cross-Linked between Lys 82beta1 and Lys 82beta2
Structural highlights
DiseaseHBB_HUMAN Defects in HBB may be a cause of Heinz body anemias (HEIBAN) [MIM:140700. This is a form of non-spherocytic hemolytic anemia of Dacie type 1. After splenectomy, which has little benefit, basophilic inclusions called Heinz bodies are demonstrable in the erythrocytes. Before splenectomy, diffuse or punctate basophilia may be evident. Most of these cases are probably instances of hemoglobinopathy. The hemoglobin demonstrates heat lability. Heinz bodies are observed also with the Ivemark syndrome (asplenia with cardiovascular anomalies) and with glutathione peroxidase deficiency.[1] [2] [3] [4] Defects in HBB are the cause of beta-thalassemia (B-THAL) [MIM:613985. A form of thalassemia. Thalassemias are common monogenic diseases occurring mostly in Mediterranean and Southeast Asian populations. The hallmark of beta-thalassemia is an imbalance in globin-chain production in the adult HbA molecule. Absence of beta chain causes beta(0)-thalassemia, while reduced amounts of detectable beta globin causes beta(+)-thalassemia. In the severe forms of beta-thalassemia, the excess alpha globin chains accumulate in the developing erythroid precursors in the marrow. Their deposition leads to a vast increase in erythroid apoptosis that in turn causes ineffective erythropoiesis and severe microcytic hypochromic anemia. Clinically, beta-thalassemia is divided into thalassemia major which is transfusion dependent, thalassemia intermedia (of intermediate severity), and thalassemia minor that is asymptomatic.[5] Defects in HBB are the cause of sickle cell anemia (SKCA) [MIM:603903; also known as sickle cell disease. Sickle cell anemia is characterized by abnormally shaped red cells resulting in chronic anemia and periodic episodes of pain, serious infections and damage to vital organs. Normal red blood cells are round and flexible and flow easily through blood vessels, but in sickle cell anemia, the abnormal hemoglobin (called Hb S) causes red blood cells to become stiff. They are C-shaped and resembles a sickle. These stiffer red blood cells can led to microvascular occlusion thus cutting off the blood supply to nearby tissues. Defects in HBB are the cause of beta-thalassemia dominant inclusion body type (B-THALIB) [MIM:603902. An autosomal dominant form of beta thalassemia characterized by moderate anemia, lifelong jaundice, cholelithiasis and splenomegaly, marked morphologic changes in the red cells, erythroid hyperplasia of the bone marrow with increased numbers of multinucleate red cell precursors, and the presence of large inclusion bodies in the normoblasts, both in the marrow and in the peripheral blood after splenectomy.[6] FunctionHBB_HUMAN Involved in oxygen transport from the lung to the various peripheral tissues.[7] LVV-hemorphin-7 potentiates the activity of bradykinin, causing a decrease in blood pressure.[8] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedA number of ligand binding studies of human adult hemoglobin (HbA) cross-linked between Lys 82beta(1) and Lys 82beta(2) with bis(3,5-dibromosalicyl)fumarate have been reported. The oxygen binding properties of native HbA, including the cooperativity and Bohr effect, are not substantially changed by the modification, provided care is taken to remove electrophoretically silent impurities arising from side reactions. We have refined the high-resolution structure of this modified Hb and found it adopts the T state when crystallized in the absence of heme ligands, contrary to a previously published structure. These results suggest the slightly altered crystal form determined previously may be due to unremoved side products of the cross-linking reaction with high oxygen affinity. Two nickel-substituted Hbs cross-linked in the same way have also been crystallized in the presence of carbon monoxide, which binds only to the ferrous heme. In the case of the nickel-substituted alpha subunit, the absence of a covalent link between the central metal of the heme and the proximal histidine leads to a new conformation of the histidine stabilized by a water molecule. This structure may mimic that of partially NO-liganded species of HbA; however, overall, the changes are highly localized, and both doubly ligated species are in the T conformation. Crystal structures of unliganded and half-liganded human hemoglobin derivatives cross-linked between Lys 82beta1 and Lys 82beta2.,Park SY, Shibayama N, Hiraki T, Tame JR Biochemistry. 2004 Jul 13;43(27):8711-7. PMID:15236579[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. Loading citation details.. Citations No citations found See AlsoReferences
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