Abstract

Hemoglobin G. Ferrara is an abnormal human hemoglobin in which an asparagine residue is replaced by a lysyl residue at position beta57 (beta57 Asn replaced by Lys). Oxygen equilibria show that cooperativity and alkaline Bohr effect are maintained to normal levels while the acid Bohr effect appears increased; in addition, a smaller effect of diphosphoglycerate is also observed. Flash photolysis experiments performed as a function of protein concentration show that the fraction of quickly reacting form is always higher than that of human hemoglobin A. This fact, together with the increase of the oxygen affinity observed at acid pH values, may be related to an enhanced dissociation of the molecule into dimers. Several attempts to isolate the native chains by treatment of the protein with p-chloromercuribenzoate were unsuccessful due to the great instability of the isolated variant beta-chains, which precipitated completely during incubation with p-chloromercuribenzoate. Therefore, although the substitution is on the surface of the molecule, there are several properties of hemoglobin G. beta Ferrara which are clearly different from hemoglobin A.