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Characterization of hemoglobin bassett (α94Asp→Ala), a variant with very low oxygen affinity
Author(s) -
Abdulmalik Osheiza,
Safo Martin K.,
Lerner Norma B.,
Ochotorena Josiree,
Daikhin Evgueni,
Lakka Vinaysagar,
Santacroce Rosa,
Abraham Donald J.,
Asakura Toshio
Publication year - 2004
Publication title -
american journal of hematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.456
H-Index - 105
eISSN - 1096-8652
pISSN - 0361-8609
DOI - 10.1002/ajh.20184
Subject(s) - bohr effect , hemoglobin , chemistry , cooperativity , globin , peptide , high performance liquid chromatography , oxygen , chromatography , microbiology and biotechnology , biochemistry , biology , organic chemistry , oxygen–haemoglobin dissociation curve
Hemoglobin (Hb) Bassett, an abnormal Hb variant with a markedly reduced oxygen affinity, was discovered in a Caucasian (Anglo‐Saxon) male child who experienced episodes of cyanosis. Cation‐exchange and reversed‐phase (RP) high‐performance liquid chromatography (HPLC) showed that the patient has an abnormal Hb, with a mutation in the α‐globin. Tryptic peptide digest of the abnormal α‐globin with subsequent HPLC analysis revealed abnormal elution of the α‐T11 peptide. Further studies with Edman sequencing and electrospray mass spectrometry of tryptic peptide α‐T11, as well as structural analysis by X‐ray crystallography revealed an Asp→Ala substitution at the α94 (G1) position, a match for Hb Bassett. Detailed functional studies showed that this Hb variant had a markedly reduced oxygen affinity ( P 50 at pH 7.0 = 22 mmHg; Hb A P 50 = 10.5 mmHg), reduced Bohr effect (−0.26 compared to − 0.54 in Hb A), and low subunit cooperativity ( n = 1.4, compared to 2.6 in Hb A). X‐ray crystallography results explain the probable effects of the structural modification on the oxygen‐binding properties of this Hb variant. Am. J. Hematol. 77:268–276, 2004. © 2004 Wiley‐Liss, Inc.