The Hb Tarrant [α126(H9)Asp→Asn] Mutation is Localized in the α2-Globin Gene

Abstract

Hb Tarrant [αl26(H9)Asp→Asn] is an abnormal variant with high oxygen affinity and decreased cooperativity in the absence of 2,3-diphosphoglycerate (2,3-DPG) and a normal Bohr effect (1,2). At room temperature, it migrates close to Hb F on cellulose acetate electrophoresis at pH 8.6 and shows a hybrid formation at 4°C (1,3). The biochemical studies showed a substitution of asparagine for aspartic acid at codon 126 in the α chain; this substitution suggested a GAC→AAC transition at an undefined α-globin gene (1-4). Hb Tarrant was previously detected in four families with Mexican ancestors, but molecular studies were not performed (2-4).