Hb T-Cambodia, a β Chain Variant with the Mutations of Hb E and Hb D-Punjab, Confirmed by DNA Analysis

Abstract

Hemoglobin variants with two amino acid substitutions affecting one globin chain are relatively rare. Hb T-Cambodia, a doubly substituted β-globin variant, was characterized previously by amino acid sequencing as having sequence alterations in β26(β8)Glu→Lys and β121(GH4)Glu→Gln (1). It is a variant that migrates cathodic to Hb A₂ on alkaline electrophoresis and with Hb A on acid citrate agar electrophoresis. We report here the mutations of Hb T-Cambodia at the nucleotide level using DNA sequencing, in β-globin gene codon 121 (GAA→CAA) and in codon 26 (GAG→AAG). These are the mutations of Hb D-Punjab and Hb E, respectively.