Structural Analysis of the Minor Human Hemoglobin Components: Hb AIa1, Hb AIa2 and Hb AIb

Laura M. GARRICK, Melisenda J. McDONALD, Robert SHAPIRO, Margaret BLEICHMAN, Michael McMANUS, H. Franklin BUNN

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Human hemolysate contains several minor hemoglobin components, including Hb AIa1, Hb AIa2, Hb AIb and Hb AIc which are post‐translational modifications of the major component, Hb Ao. Hb AIc is known to contain glucose attached to the N terminus of the β chains by a ketoamine linkage. We separated the α and β globin chains from purified Hb Ia1, Hb AIa2 and Hb A Ib by ion‐exchange chromatography. The β chains were reducible by sodium borohydride and gave a positive thiobarbituric acid test. These results indicated that they are modified by ketoamine‐linked carbohydrate. In addition, phosphate analysis revealed 1.5 phosphate residue associated with each β AIa1 chain and 1 phosphate residue with each β AIa2 chain. Hb AIa1, Hb AIa2 and Hb AIb were all found to be contaminated by non‐globin proteins. Protein‐sequencing approaches demonstrated that the N termini of β AIa1, β AIa2 and β AIb were blocked. In support of this conclusion, analysis of tryptic digests of β AIa2 and β AIb revealed modified N‐terminal peptides. We conclude that, like Hb AIc, components Hb AIa1, Hb AIa2 and Hb AIb also contain a sugar moiety linked to the N terminus of the β chain.

Original languageEnglish
Pages (from-to)353-359
Number of pages7
JournalEuropean Journal of Biochemistry
Volume106
Issue number2
DOIs
StatePublished - May 1980
Externally publishedYes

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