Subunit structure and reassembly of mega-hemocyanin. (a) SDS-PAGE of Leptoxis carinata hemocyanin (LcH); note the constant ratio of the two subunits in the different individuals. (b) SDS-PAGE of whole Terebralia palustris hemocyanin (TpH, sample 1), and of gel filtration chromatography fractions enriched in mega-tridecamers (sample 2) and typical didecamers (sample 3), respectively. M, myosin marker (205 kDa) (c) SDS-PAGE of intact Terebralia hemocyanin ("control", left lane) and of Terebralia hemocyanin after limited tryptic cleavage for 3 hours ("cleavage", right lane); note occurrence of two subunit fragments derived from the 550 kDa subunit. (d) SDS-PAGE of Melanoides tuberculata hemocyanin (MtH); note variable ratio of the two subunits in the different individuals. (e) Crossed immunoelectrophoresis (IE) of Melanoides tuberculata hemocyanin (MtH, sample 6 in d), showing that the two subunits are immunologically distinct. (f) Tandem-crossed immunoelectrophoresis (samples 6 and 7 in d) to identify both peaks. (g, h) Reassembly experiments with the individual MtH subunits; note exclusive formation of mega-decamers in g, and of typical hemocyanin oligomers in h.