Asymetric tetramer in a second occurrence of hemoglobin Porto Alegre alpha A2betaAbeta9Ser replaced by Cys.

Hemoglobin Porto Alegre is an abnormal human hemoglobin which polymerizes by formation of intermolecular disulfide bonds between the mutant cysteinyl residues at the beta9 position. Biochemical studies of this abnormal hemoglobin from a heterozygous carrier of a second family of carriers indicates that an asymmetric tetramer alphaA2betaAbeta9 Ser replaces Cys is formed after polymerization. Functional studies of the polymer indicate that its oxygen binding properties are unaffected by the polymerization and that its oxygen affinity is somewhat higher than that of normal hemoglobin; it has a slightly reduced heme-heme interaction and a normal Bohr effect.