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Hb Sitia [beta128(H6)Ala-->Val]: an unstable variant with a substitution in the alpha1beta1 interface
I Papassotiriou1, J Traeger-Synodinos, D Promé
1Department of Clinical Biochemistry, Aghia Sophia Children's Hospital, Athens, Greece.
Abstract:
Hb Sitia [beta128(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 beta-globin chain. Since alanine at beta128(H6) interacts with several amino acids of the alpha1beta1 contact, its replacement by a larger residue results in a mild instability of the molecule and slight modifications of the oxygen binding properties.