N-terminal amino acid sequence comparison of asian horseshoe crab hemocyanins: Immunologically identical hemocyanin subunits are orthologous in asian horseshoe crabs

Abstract

Each hemocyanin of the 3 Asian horseshoe crabs is composed of 6 immunologically different subunits, each subunit of which is immunologically identical with the comparable subunits of 2 other species. These immunologically identical subunits show 0-15% N-terminal sequence differences between Carcinoscorpius rotundicauda and Tachypleus gigas, while the immunologically different subunits show 25-74% sequence differences within species and 25-72% between C. rotundicauda and T. gigas. From the N-terminal sequence comparison and immunological comparison of hemocyanin subunits, it is evident that Asian horseshoe crabs share 6 orthologous hemocyanin subunits which are immunologically identical. We may produce 6 phylogenetic trees of Asian horseshoe crabs using the 6 sets of orthologous hemocyanin subunits and an evolutionary tree of horseshoe crab's hemocyanin molecules.