Quantities of αQ chain variants in heterozygotes with and without a concomitant β‐thalassemia trait

We have analyzed the quantities of αx chain-containing hemoglobins (αxβ2 and α2xβ2,) in 14 heterozygotes for Hb Q-India [α64(E13)AspHis] or Hb Q-Thalland [α74(EF3)AspHls]; both amino acid replacements are the result of mutations in the α1-globin gene. Five of these persons (three with Hb Q-India and two with Hb Q-Thailand) had an additional β°-thalassemia heterozygoslty. The average quantities for Hb Q + Hb Q2 in the four groups were 17.2% (Q/αα; βA/βA), 9.5% (ααQ/αα; βA/β°Th), 26.8% (-αQ/αα;βA/βA), and 16.95% (-αQ/αα; βA/β°Th). These variations can best be explained by a posttranslational control mechanism; an imbalance in the αA, αQ, and βA chain ratio will favor the αzQβz formation when an α-thalassemia is present and will reduce its formation in the presence of a β-thalassemia heterozygosity. © 1994 Wiley-Liss, Inc.