A mass spectrometric study of the heterogeneity of the monomer subunit of Lumbricus terrestris hemoglobin

• Published in: Journal of the American Society for Mass Spectrometry 1997-04, Vol.8 (4), p.352-364
• Main Authors: Maier, Claudia S., Arbogast, Brian, Hahn, Ulrike, Deinzer, Max L., Kuchumov, Askar R., Vinogradov, Serge N., Walz, Daniel A.
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chains; Fundamental and applied biological sciences. Psychology; Hemoglobin; Hemoproteins; Heterogeneity; High performance liquid chromatography; Homology; Mass spectrometry; Metalloproteins; Molecular chains; Molecular weight; Monomers; Proteins; Spectrometry
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/S1044-0305(96)00281-4

The subunits of the hemoglobin of Lumbricus terrestris consist of heme-binding globin chains, designated a, b, c, and d, and linker chains. The sequence of chain d, which is also referred to as a monomer subunit, has been reported by Shishikura et al. ( Biol. Chem. 1987, 262, 3123–3131). This subunit has been found to be heterogeneous and in this study three fractions were separated by C 18 reverse-phase high-performance liquid chromatography. The major chain d 1 with molecular weight 15,993.5 ± 2.1 u possesses S 7 instead of G 7, the partial sequence RDIIDD (33–38) instead of KGILRE, E instead of Q in positions 23 and 58, and T 84 instead of A 84. The C-terminus is K 140 instead of D 141I 142. Chain d 3 with molecular weight 15,963.2 ± 1.6 u showed high sequence homology with chain d 1, differing apparently only in residue 84 where A 84 replaces T 84. Analysis of the third chromatographie fraction revealed two additional chains with molecular weights of 15,996.1 ± 1.4 and 15,937.6 ± 1.2 u. These are designated chains d 2 and d 4, respectively, but their sequence assignments are not yet certain.