Hemoglobin J Altgeld Gardens. A hemoglobin variant with a substitution of the proximal histidine of the beta-chain.
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A case of hemoglobin H disease in combination with hemoglobin Constant Spring and a beta-globin chain variant is reported in a 3-yr-old Thai girl. On routine cellulose acetate electrophoresis, one abnormal band in addition to the hemoglobins A, A2, H, Bart's and Constant Spring was detected. The amount of this abnormal band movement towards more anodic to the hemoglobin A was 35.7%. DNA analysis of the alpha-globin gene cluster by polymerase chain reaction (PCR) revealed a combination of defects caused by the SEA-type alpha-thalassemia 1 and the alpha-Constant Spring gene. Analysis of beta-globin gene by PCR and DNA sequencing also detected the heterozygosity for the GGC-GAC mutation at codon 56, leading to a substitution of aspartic acid for glycine resulting in the hemoglobin J Bangkok. The hematologic data of this unusual case of hemoglobin H disease are presented and compared with two compound heterozygotes for hemoglobin J Bangkok and alpha-thalassemia 1 found in the patient's father and grandfather. A simple DNA assay based on an allele-specific PCR for rapid diagnosis of the hemoglobin J Bangkok is also described.
Polycythemia in carriers of hemoglobin J Cape Town or hemoglobin Chesapeake is thought to be produced by increased oxygen affinity of their blood. Both hemoglobins involve substitution of amino acid residue alpha FG-4. Measurements reported here, of the oxygen equilibrium of purified hemoglobin J Cape Town, permit direct comparison of the two hemoglobins. J Cape Town exhibits lower oxygen affinity, and greater heme-heme interaction, than Chesapeake; both exhibit normal Bohr effects. Substitution of one polar amino acid residue for another of opposite charge (arginine --> glutamic acid) thus appears to create less disruption of the interface between alpha- and beta-chains than substitution of a nonpolar residue (arginine --> leucine).
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Hemoglobin J Capetown was found incidentally in a patient of french origin suffering from urticaria with delayed pressure oedema. Using a preparative finger-print technique, the structural determination was easy. A functional study of the purified component confirmed the high oxygen affinity of hemoglobin J Capetown and demonstrated a low reactivity for organic phosphates. These results may explain the perturbations observed in the whole blood.
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Hemoglobin J (HbJ), Guantanamo, which had been described but once in the literature, was found in a family originating from Benin; this second case was found to be in association with hemoglobin C (HbC) and alpha-thalassemia. High-performance liquid chromatography (HPLC) procedures and microsequencing were used for characterization of the aminoacid substitution. The main hematological disorder, in relation with the instability of Hb J Guantanamo, seems to be a worsening of the rheological properties of the red blood cells (RBC), as demonstrated by ektacytometric studies. Oxygen-binding properties of the RBC were almost normal, but a slight decrease in cooperativity and lowered Bohr and 2,3-diphosphoglycerate (DPG) effects were observed for pure stripped Hb J Guantanamo. The expression of the electrophoretic charge difference was partly masked, as is often observed when the structural abnormality is situated in or near a contact area.
Hemoglobin J Sardegna [alpha50(CD8)His-->Asn -->Asp] is a human Hb variant in which a posttranslational deamidation process takes place, transforming an Asn to an Asp residue. This variant, particularly widespread in northern Sardinia, has for the first time been characterized at the DNA level (codon 50 C-->A) on the selectively amplified alpha2-globin gene. We determined the protein and DNA sequences and performed cellulose acetate electrophoresis, isoelectric focusing, globin chain separation, stability tests with isopropanol and heat precipitation, and oxygen affinity analyses on whole blood to fully characterize the variant. A comprehensive review of the deamidation processes involving Asn and Gln residues in mutant proteins is reported, together with a discussion of the molecular mechanisms of such deamidations. Finally, examples of other proteins of clinical importance in which Asn or Gln residues have been implicated by DNA analysis alone are presented. These findings point out the importance of the complete characterization of variant proteins by use of both DNA and protein analyses.
The present report describes clinical, hematological and biochemical studies of a 27-year old Egyptian woman in whom a fast moving Hb variant was found. The abnormal Hb constituted 48% of the total erythrocyte Hb of the propositus and her father. Structural studies demonstrated that in the abnormal Hb lysine beta 65 is replaced by glutamine. The new Hb mutant is designated hemoglobin J Cairo beta 65 (E9) Lys leads to Gln. This substitution results in only a moderate decrease in cooperativity. No evidence of Hb instability was found. A slight anemic state has been observed in the propositus since she reached adolescence.
Hemoglobin J Mexico, an alpha chain mutant, was studied in eight unrelated Algerian families. The quantities of the abnormal hemoglobin in 116 subjects are trimodally distributed: 55% in homozygotes, 31% and 38% in heterozygotes. Both hematological data and the alpha/beta chain biosynthetic ratio are normal in heterozygotes with 31% Hb J and in homozygotes. In contrast, the MCV and MCH as well as the alpha/beta biosynthetic ratio are slightly reduced in heterozygotes with 38% Hb J and in their relatives carrying Hb A. The elevated expression of alphaJ chains in heterozygotes with 38% Hb J may be due to an alpha thalassemia gene trans to the alphaJ locus.
Hemoglobin J Mexico has been found in five generations of a large Algerian family. Nine subjects have 55% Hb J although their parents, siblings and offspring may have 31%, the usual quantity found in heterozygotes. Those with 55% Hb J are considered to be homozygous for a chromosome carrying both a normal alpha chain locus and a locus for alphaJ. The proportion of the abnormal hemoglobin in all the subjects is in favor of an unequal expression of both loci, the amount of protein synthesis directed by the alpha J gene being greater than that directed by the alpha A. In two heterozygotes a slightly higher proportion of the Hb J (38%) suggests the presence of a single normal alpha chain locus in trans. An associated alpha-thalassemia was excluded by biosynthetic studies in this family.
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The cas observed in Auvergne and reported here raises the aetiological problem of polycythaemias. Young subjects with polycythaemia should be investigated for congenital anomaly of oxygen transport by measuring P50 and 2,3-DPG, which provides information on the oxygen-carrying capacity of haemoglobin. When confronted with familial polycythaemia due to high oxygen affinity haemoglobin, clinicians must know that a cause-effect relationship is not always demonstrable since other factors, such as tobacco-smoking in this particular case, may intervene.
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A new abnormal hemoglobin, Hb J Amiens beta 17 (A 14) Lys replaced by Asn, has been discovered during the exploration of a recent polycythemia in a 65-year-old patient of Spanish extraction. Oxygen affinity of washed red blood cells was found to be normal at pH 7.13 (P 50 = 30.0 mmHg, N = 29.5 +/- 1). Cooperativity is unchanged, and no instability was detected. From this study, it is concluded that there is no relation between this functionally silent hemoglobin and the polycythemia. In fact, the recent appearance of the polycythemia, the involvement of the other blood cell lines, particularly the thrombocytosis, the high score of leukocyte alkaline phosphatases, and the results of the bone marrow biopsy led to the diagnosis of polycythemia vera.
We report a new case of hemoglobin J. Broussais, present in its heterozygote form in a seven year old child from Martinque. The structural characteristics of this abnormal hemoglobin have been compared by three methods: 1. By analytical and preparative finger-printing on silica gel thin layer plates after tryptic digestion. 2. By a programmed separation of tryptic peptides on various ion exchange resins. 3. And by automatic sequencing of the peptides obtained following CNBr cleavage and separation by gel filtration chromatography. The functional behaviour of this hemoglobin was not modified by the substitution of an Asn for a Lys residue at position 90, although its presence induced slight hematological disorders in the patient. Abnormal hemoglobins which have been identified in Martinique and Guadeloupe are reviewed.
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