title: Hb Arta [beta 45 (CD4) Phe-->Cys]: a new unstable haemoglobin with reduced oxygen affinity in trans with beta-thalassaemia.
abstract: The interaction of rare Hb variants with beta(0)-thalassaemia results in a quasihomozygous state where the erythrocytes contain the variant as the only major adult Hb component. Such a situation is a unique model that enables functional studies even in the case of a neutral variant that could not be isolated from Hb A. We report here an unusual patient carrying Hb Arta, a novel Hb variant [beta 45 (CD4) Phe-->Cys], in trans with beta(0)-thalassaemia gene (beta(0) 39). The aminoacid substitution at the critical CD corner of this Hb molecular renders the molecule unstable. In addition, haem is displaced in a position that favours the deoxy (T) conformation of the variant, but less than in Hb Cheverly [beta 45 (CD4) Phe-->Ser], and results in a p50 of 43 mmHg (pH 7.4, 37 degrees C) in the red cells with preservation of cooperativity. Solution studies of the almost pure Hb Arta show a 50% decrease in oxygen affinity and normal cooperativity; the Bohr effect and the interaction with organic phosphates are similar to those of Hb A. Hb Arta retains both normal homo- and heterotropic effects allowing a well-preserved oxygen transport in vivo despite a mild anaemia.
authors.affiliation: First Department of Medicine, Laikon Hospital, Athens, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Vassilopoulos
authors.forename: I
authors.initials: I
authors.lastname: Papassotiriou
authors.forename: E
authors.initials: E
authors.lastname: Voskaridou
authors.forename: A
authors.initials: A
authors.lastname: Stamoulakatou
authors.forename: E
authors.initials: E
authors.lastname: Premetis
authors.forename: J
authors.initials: J
authors.lastname: Kister
authors.forename: M
authors.initials: M
authors.lastname: Marden
authors.forename: N
authors.initials: N
authors.lastname: Griffon
authors.forename: C
authors.initials: C
authors.lastname: Poyart
authors.forename: H
authors.initials: H
authors.lastname: Wajcman
mesh_terms: D000328:Adult; D001483:Base Sequence; D004247:DNA / Q000032:analysis; D004588:Electrophoresis, Cellulose Acetate; D005260:Female; D006455:Hemoglobins, Abnormal / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D017086:beta-Thalassemia / Q000097:blood / Q000235:genetics*
chemical_list: D006455:Hemoglobins, Abnormal; D004247:DNA; D010100:Oxygen