alpha Chain mutations with opposite effects on the gelation of hemoglobin S. 1979

R E Benesch, and S Kwong, and R Edalji, and R Benesch

The preparation of three hemoglobin tetramers containing the hemoglobin S mutation at beta 6 and an additional one at alpha 6, alpha 47, and alpha 75 is described. The effect of the substitutions in the alpha chains on polymerization was investigated by the equilibrium solubility of the gels as well as the abrupt change in oxygen affinity associated with the onset of gelation. Substitution of a histidine for aspartic acid at alpha 47 causes a marked inhibition of polymerization. This inhibition probably results from tetramers which carry the two substitutions on the same alpha beta dimer. By contrast, the introduction of a tyrosine at alpha 75 and an alanine at alpha 6 have the opposite effect and are the first examples of alpha chain mutations which potentiate the gelation of Hb S. The molecular mechanisms responsible for the effects of the mutations on the self-association of Hb S are discussed.

UI MeSH Term Description Entries
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D005782 Gels Colloids with a solid continuous phase and liquid as the dispersed phase; gels may be unstable when, due to temperature or other cause, the solid phase liquefies; the resulting colloid is called a sol.
D006451 Hemoglobin, Sickle An abnormal hemoglobin resulting from the substitution of valine for glutamic acid at position 6 of the beta chain of the globin moiety. The heterozygous state results in sickle cell trait, the homozygous in sickle cell anemia. Hemoglobin S,Deoxygenated Sickle Hemoglobin,Deoxyhemoglobin S,Hemoglobin SS,Hemoglobin, Deoxygenated Sickle,SS, Hemoglobin,Sickle Hemoglobin,Sickle Hemoglobin, Deoxygenated
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012995 Solubility The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Solubilities
D046911 Macromolecular Substances Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure. Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular

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