Oxygenation properties and oxidation rates of mouse hemoglobins that differ in reactive cysteine content

House mice (genus Mus) harbor extensive allelic variation at two tandemly duplicated genes that encode the beta-chain subunits of adult hemoglobin (Hb). Alternative haplotypes differ in the level of sequence divergence between the two beta-globin gene duplicates: the Hbb(d) and Hbb(p) haplotypes harbor two structurally distinct beta-globin genes, whereas the Hbb(s) haplotype harbors two beta-globin duplicates that are identical in sequence. One especially salient difference between the s-type Hbs relative to the d- and p-type Hbs relates to the number of reactive beta-chain cysteine residues. In addition to the highly conserved cysteine residue at beta 93, the d- and p-type Hbs contain an additional reactive cysteine residue at beta 13. To assess the functional consequences of allelic variation in beta-globin cysteine content, we measured O-2-binding properties and H2O2-induced oxidation rates of mono- and dicysteinyl beta-Hbs from 4 different inbred strains of mice: C57BL/6J, BALB/cJ, MSM/Ms, and CAROLI/EiJ. The experiments revealed that purified Hbs from the various mouse strains did not exhibit substantial variation in O-2-binding properties, but s-type Hb (which contains a single reactive beta-chain cysteine residue) was far more readily oxidized to Fe3+ metHb by H2O2 than other mouse Hbs that contain two reactive beta-chain cysteine residues. These results suggest that the possession of an additional reactive cysteine residue may protect against metHb formation under oxidizing conditions. The allelic differences in beta-globin cysteine content could affect aspects of redox signaling and oxidative/nitrosative stress responses that are mediated by Hb-S-nitrosylation and Hb-S-glutathionylation pathways. (C) 2011 Elsevier Inc. All rights reserved.