Open AccessStructural Analysis of the Minor Human Hemoglobin Components: Hb A Ia1 , Hb A Ia2 and Hb A Ib
Author(s) -
GARRICK Laura M.,
McDONALD Melisenda J.,
SHAPIRO Robert,
BLEICHMAN Margaret,
McMANUS Michael,
BUNN H. Franklin
Publication year - 1980
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1980.tb04581.x
Subject(s) - chemistry , hemoglobin , residue (chemistry) , borohydride , globin , beta (programming language) , hemoglobin variants , stereochemistry , biochemistry , computer science , programming language , catalysis
Human hemolysate contains several minor hemoglobin components, including Hb A Ia1 , Hb A Ia2 , Hb A Ib and Hb A Ic which are post‐translational modifications of the major component, Hb A o . Hb A Ic 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 A Ia2 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 A Ia1 chain and 1 phosphate residue with each β A Ia2 chain. Hb A Ia1 , Hb A Ia2 and Hb A Ib were all found to be contaminated by non‐globin proteins. Protein‐sequencing approaches demonstrated that the N termini of β A Ia1 , β A Ia2 and β A Ib were blocked. In support of this conclusion, analysis of tryptic digests of β A Ia2 and β A Ib revealed modified N‐terminal peptides. We conclude that, like Hb A Ic , components Hb A Ia1 , Hb A Ia2 and Hb A Ib also contain a sugar moiety linked to the N terminus of the β chain.