Polymorphic hemoglobin from a midge larva (Tokunagayusurika akamusi) can be divided into two different types

The hemoglobin from the 4th-instar larva of Tokunagayusurika akamusi, a common midge found in eutrophic lakes in Japan, was composed of as many as 11 separable components (IA, IB, II, III, IV, V, VIA, VIB, VII, VIII, IX) on a DEAE-cellulose column. However, we have found that these components can be divided into two groups on the basis of their spectroscopic properties, one being named as the normal type (N-type) and the other being referred to as the low type (L-type). Since the major difference between them seemed to be the presence or absence of the distal (E7) histidine residue, which plays an important role in the stability properties of the bound dioxygen, the complete amino acid sequence was then determined for each typical component, namely, VII (N-type) and V (L-type): the former hemoglobin contained the usual distal histidine residue at position 64, whereas the latter one replaced it by isoleucine at position 66. The homology test for 40 N-terminal amino acid residues of all components also demonstrates that T. akamusi hemoglobin is composed of two different clusters showing a very early separation in the phylogenetic tree.