title: Structural and Functional Characterization of a New Double Variant Haemoglobin (HbG-Philadelphia/Duarte α(2)β(2)).
abstract: WE REPORT THE FIRST CASE OF COSEGREGATION OF TWO HAEMOGLOBINS (HBS): HbG-Philadelphia [α68(E17)Asn → Lys] and HbDuarte [β62(E6)Ala → Pro]. The proband is a young patient heterozygous also for β°-thalassaemia. We detected exclusively two haemoglobin variants: HbDuarte and HbG-Philadelphia/Duarte. Functional study of the new double variant HbG-Philadelphia/Duarte exhibited an increase in oxygen affinity, with a slight decrease of cooperativity and Bohr effect. This functional behaviour is attributed to β62Ala → Pro instead of α68Asn → Lys substitution. Indeed, HbG-Philadelphia isolated in our laboratory from blood cells donor carrier for this variant is not affected by any functional modification, whereas purified Hb Duarte showed functional properties very similar to the double variant. NMR and MD simulation studies confirmed that the presence of Pro instead of Ala at the β62 position produces displacement of the E helix and modifications of the tertiary structure. The substitution α68(E17)Asn → Lys does not cause significant structural and dynamical modifications of the protein. A possible structure-based rational of substitution effects is suggested.
authors.affiliation: Department of Sciences Applied to Biosystems, University of Cagliari, S.P. Monserrato-Sestu km 0.700, 09042 Monserrato, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Fais
authors.forename: Mariano
authors.initials: M
authors.lastname: Casu
authors.forename: Paolo
authors.initials: P
authors.lastname: Ruggerone
authors.forename: Matteo
authors.initials: M
authors.lastname: Ceccarelli
authors.forename: Simona
authors.initials: S
authors.lastname: Porcu
authors.forename: Benedetta
authors.initials: B
authors.lastname: Era
authors.forename: Roberto
authors.initials: R
authors.lastname: Anedda
authors.forename: Maria Carla
authors.initials: MC
authors.lastname: Sollaino
authors.forename: Renzo
authors.initials: R
authors.lastname: Galanello
authors.forename: Marcella
authors.initials: M
authors.lastname: Corda
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