Abstract
Hb Sitia [β128(H6)Ala → Val] was found in a Greek female with slightly reduced red blood cell indices. The abnormal hemoglobin was indistinguishable from Hb A by electrophoresis but eluted after Hb A on cation exchange high performance liquid chromatography. DNA sequence analysis revealed a GCT → GTT mutation at codon 128, which is predicted to encode an Ala → Val substitution. This was confirmed by mass spectrometry analyses of the β-globin chain. Since alanine at β128(H6) interacts with several amino acids of the α1β1 contact, its replacement by a larger residue results in a mild instability of the molecule and slight modifications of the oxygen binding properties.