RESUMO
Hb Crete, an electrophoretically neutral, unstable, high oxygen affinity variant, was characterized by protein and DNA analyses in the homozygous state in a 32-year-old woman from Crete, with erythrocytosis and microcytosis. The proband and members of her family over 3 generations, including 5 carriers of Hb Crete, were subject to clinical, hematological and biochemical investigations, and DNA, RNA and protein studies were carried out. The proband demonstrated features associated with disturbed hemoglobin (Hb) structure and function, including erythrocytosis and additionally a state of functional anemia, the latter reflected by increased erythropoetin levels and cardiac output. In addition, all the carriers surprisingly had hematological and biosynthetic findings more usually associated with thalassemia trait. The structural change in Hb Crete only partly explains all the pathological manifestations of this variant, and other mechanisms are discussed.
Assuntos
Anemia/genética , Hemoglobinas Anormais/genética , Policitemia/genética , Adulto , Monóxido de Carbono/metabolismo , Débito Cardíaco , Eritropoetina/sangue , Saúde da Família , Feminino , Hemoglobinas Anormais/metabolismo , Homozigoto , Humanos , Cinética , Linhagem , Fenótipo , TalassemiaAssuntos
Hemoglobinas Anormais/química , Hemoglobinas Anormais/genética , Mutação de Sentido Incorreto , Oxigênio/metabolismo , França , Variação Genética , Globinas/química , Globinas/genética , Hemoglobinas Anormais/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Estrutura Quaternária de ProteínaAssuntos
Hemoglobinas Anormais/genética , Oxigênio/metabolismo , Mutação Puntual , Adulto , Sequência de Bases , Sítios de Ligação/genética , Cromatografia Líquida de Alta Pressão , Variação Genética , Heme , Hemoglobinas Anormais/química , Hemoglobinas Anormais/metabolismo , Humanos , Focalização Isoelétrica , MasculinoRESUMO
Hb O-Tibesti, carries in the same chain the substitution of Hb O-Arab [beta121(GH4)Glu-->Lys] and that of Hb Hamilton [beta11(A8)Val-->Ile]. Hb O-Tibesti may be distinguished from Hb O-Arab by polyacrylamide gel electrophoresis in the presence of urea and Triton-X100, and by reversed phase high performance liquid chromatography. It was found in a compound heterozygous condition with Hb S [beta6(A3)Glu-->Val] in a child of Chad-Sudanese descent, suffering from a sickle cell syndrome. Compared to the classical description of the Hb S/Hb O-Arab association, the additional Hb Hamilton mutation does not seem to modify the clinical presentation.
Assuntos
Substituição de Aminoácidos , Globinas/genética , Hemoglobina Falciforme/genética , Hemoglobinas Anormais/química , Hemoglobinas Anormais/isolamento & purificação , Traço Falciforme/genética , Eletroforese das Proteínas Sanguíneas , Chade/etnologia , Criança , Cromatografia Líquida de Alta Pressão , França , Globinas/química , Hemoglobinas Anormais/genética , Heterozigoto , Humanos , Interações Hidrofóbicas e Hidrofílicas , Masculino , Sudão/etnologiaRESUMO
The effects of the mutation beta9(A6)Ser --> Cys on the interactions between the human hemoglobin molecules were investigated, and comparisons were made with other variants having an additional cysteine residue. In hemoglobin Porto Alegre (PA), the beta9 mutation induces polymerization by forming interchain disulfide bonds via the extra cysteine. The hemolysate from a heterozygote was separated by gel filtration into a tetrameric fraction and a higher-molecular-weight oligomeric fraction (30%). Reversed-phase high-performance liquid chromatography and electrospray ionization mass spectrometry (ESI-MS) under denaturing conditions showed that the tetrameric fraction contained only normal alpha- and beta-chains, whereas the oligomeric fraction contained only normal alpha-chain and disulfide-linked beta(PA) dimer. Under native conditions, ESI-MS of the oligomeric fraction revealed a principal complex of mass 258,400 Da corresponding to a tetramer of tetramers, and 10% of minor components. Transmission electron microscopy corroborated this structure by showing four spheres of 140 A diameter surrounding a central cavity. Equilibrium experiments on the oligomer at different concentrations, using gel filtration and dimer exchange experiments with metHbA-CN, showed that the tetramer of tetramers dissociates into smaller species, probably by breaking the dimer-dimer allosteric interface. None of the other variants investigated formed such a large oligomer.
