Hb Ashburton [β12(A9)Thr → Pro; HBB: c.37A > C], a novel, mildly unstable variant and the first substitution identified at codon 12.
We report the identification of a novel, slightly unstable hemoglobin (Hb) variant [β12(A9)Thr → Pro; HBB: c.37A > C] that came to our attention during Hb A1C ion exchange chromatography where it migrated as a trailing shoulder on the Hb A0 peak. On electrospray ionization mass spectrometry (ESI MS), this electrophoretically silent variant was detected as an unresolved β component with a 2 Da decrease in average β chain mass. Reversed phase high performance liquid chromatography (HPLC) confirmed the presence of a more hydrophilic β chain with a mass 4 Da less than normal β(A) and showed it represented 40.0% of the total β-globin. Tryptic mapping revealed the [M + 1H] ion of peptide βT-2 had shifted from 932.5 to 928.5 m/z, suggesting a point mutation of Thr → Pro at position β12(A9). This substitution was confirmed by fragmentation analysis of the [M + 2H] ion (464.8 m/z) of the new βT-2 peptide and it represents a novel mutation which we have named Hb Ashburton.
Molecular Pathology Laboratory, Canterbury Health Laboratories , Christchurch , New Zealand.
Stephen O
SO
Brennan
Anthea
A
Povall
Ulrich
U
Lankes
D000368:Aged; D002851:Chromatography, High Pressure Liquid; D003062:Codon / Q000235:genetics*; D006455:Hemoglobins, Abnormal / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D020125:Mutation, Missense; D009842:Oligopeptides; D011392:Proline / Q000235:genetics; D021241:Spectrometry, Mass, Electrospray Ionization; D013912:Threonine / Q000235:genetics; D055544:beta-Globins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D003062:Codon; D006455:Hemoglobins, Abnormal; D009842:Oligopeptides; D055544:beta-Globins; C000593190:hemoglobin Ashburton; C056080:ES 1005; D013912:Threonine; D011392:Proline