Hemoglobins, XXXIX. Amino acid sequence of a dimeric hemoglobin (erythrocruorin) from Chironomus thummi thummi: component CTT VIII.
The globin of the homo-dimeric hemoglobin CTT VIII was isolated by chromatography of the CTT-hemoglobins on DEAE-cellulose and rechromatography of the crude CTT VIII globin on CM-cellulose. The sequence was established by automatic degradation of the globin, tryptic peptides derived from various limited tryptic digestions and one cyanogen bromide peptide. As an additional proof of the C-terminal sequence splitting with carboxypeptidase was carried out. The tryptic activity was limited by chemical modification of the epsilon-amino groups of the lysines nd the delta-guanidino groups of the arginines, respectively. A reduction of the tryptic fragments from the maleylated globin was achieved by special digestion conditions: high pH value and short digestion time. The hemoglobin consists of 2 X 151 residues with a molecular weight of 32438. The structure of CTT VIII is homologously aligned with a monomeric CTT-hemoglobin (CTT III) and the human-beta-chain. There is a conformity of 39.7% to the CTT III-hemoglobin and 13.9% to the human beta-chains. All three hemoglobins are identical in 12 positions only. The secondary structures are postulated according to the CTT III-component. Possible structural differences are discussed.