The primary structure of a dimeric insect hemoglobin (erythrocruorin), component CTT IX (Chironomus thummi thummi) was established by automatic sequence analysis. The alignment of the peptides was facilitated by producing only a few large fragments. The primary structure of CTT IX is compared with the human beta-chains and with CTT III. It is discussed, why for the dimeric CTT-hemoglobins only dimerisation can be observed but no tetramerisation. Experiments were done to locate the binding areas between the subunits in the dimeric molecule. Even after blocking of the alpha-NH2-group by cyanate, the stability of the dimeric molecule is not altered. Therefore the binding regions of the CTT-hemoglobins must be different from those of the tetrameric hemoglobins of vertebrates. Our results lead to a quarternary structure different from that of the hemoglobins of mammalians. This structure explains the possibility of dimerisation, but excludes tetramerisation.
Amino Acid Sequence Chironomidae