Identification, structure, and properties of hemocyanins from diplopod myriapoda

Hemocyanins are copper-containing, respiratory proteins that occur in the h emolymph of many arthropod species. Here we report for the first time the p resence of hemocyanins in the diplopod Myriapoda, demonstrating that these proteins are more widespread among the Arthropoda than previously thought. The hemocyanin of Spirostreptus sp, (Diplopoda: Spirostreptidae) is compose d of two immunologically distinct subunits in the 75-kDa range that are mos t likely arranged in a 36-mer (6 x 6) native molecule. It has a high oxygen affinity (P-50 = 4.7 torr) but low cooperativity (h 1.3 +/- 0,2). Spirostr eptus hemocyanin is structurally similar to the single known hemocyanin fro m the myriapod taxon, Scutigera coleoptrata (Chilopoda), indicating a rathe r conservative architecture of the myriapod hemocyanins. Western blotting d emonstrates shared epitopes of Spirostreptus hemocyanin with both chelicera te and crustacean hemocyanins, confirming its identity as an arthropod hemo cyanin.