Hb Rainier [beta 145(HC2)Tyr -> Cys] in Italy. Characterization of the amino acid substitution and the DNA mutation

A high oxygen affinity hemoglobin variant was identified in a 53-year-old m ale patient from Napoli (Italy), suffering from pulmonary thromboembolism a nd polycythemia, A detailed structural characterization of the variant hemo globin was carried out, both at the protein and DNA levels, by a combinatio n of DNA sequencing and allele-specific amplification techniques with mass spectrometric procedures. The amino acid substitution was found to be Tyr - -> Cys, and the corresponding DNA mutation was identified as A --> G at the second position of codon 145 of the beta chain, These variations indicated the presence of Hb Rainier. Haplotype analysis of DNA polymorphisms showed that the beta-globin gene from Hb Rainier was associated with haplotype II . Moreover, structural analyses provided direct identification of an intram olecular disulphide bridge joining the newly inserted beta 145Cys with beta 93Cys. This is the first report of the occurrence of Hb Rainier in Italy.