Structural comparison of TpH (type 4) with type 3 hemocyanin. (a) Three different dimer types that assemble the TpH decamer (type 4). The dimer of Nautilus hemocyanin (type 3) (EMD-1434) is also shown. Inner FUs of each subunit dimer are highlighted in color. Polar and equatorial FU-gs are colored green and cyan, respectively. FU-d*s are shown in yellow. (b) Cut-away view of the cryo-EM density of Nautilus hemocyanin (type 3). Polar and equatorial FU-gs are colored green and cyan, respectively. The wall region is shown in transparent gray. For better clarity, a schematic of the view and the density of an extracted subunit dimer are also shown.