Subunit composition and N-terminal analysis of arthropod hemocyanins

Fourteen structural subunits of hemocyanins from two different infraorders of crustacea, brachyura (Maia squinado, Carcinus maenas) and astacidea (Homarus americanus) were isolated and characterized. N-terminal amino acid sequences were determined and compared with known sequences of crustacean and cheliceratan hemocyanins. Relationships between the investigated polypeptide chains were established. The results demonstrate that the degree of identity, calculated from the amino terminal sequences, is lower than that determined from the complete sequences and can be used for reliable characterization of the whole individual subunits. Independent evolution is possible not only for members of different subphyla, but also for those from one infraorder or from the same hemocyanin.