Hemoglobins, XXXVIII. Amino acid sequence of a dimeric hemoglobin (erythrocruorin), component VI from Chironomus thummi thummi (CTT VI).

The dimeric hemoglobin CTT VI (Erythrocruorin) was isolated from the hemolymph of the larvae of Chironomus thummi thummi. The globin from CTT VI was subjected to trypsin, limited trypsin and cyanogen bromide digestion. For elucidation of the sequence in the C-terminal region, cleavage with Staphylococcus aureus V8 protease was also carried out. The peptides were separated by gel and ion-exchange chromatography. The handling of some large fragments was facilitated by maleylation and subsequent ion-exchange chromatography with conservation of the maleyl groups. The amino acid sequence was determined by automatic Edman degradation. The order of the peptides was provided by overlaps, but in two cases by homology only (for residues 98 and 99, and 109 and 110). The hemoglobin consists of 2 x 147 amino acids with a molecular weight of 32411. The sequence of CTT VI is compared with a monomeric (CTT III) and a dimeric hemoglobin (CTT II beta) and the human alpha-chains. The structural differences are discussed.