Fig. 2.
Subunits A, B and C about a quasi threefold axis are shown in blue, yellow and pink, respectively, with the difference electron density for the OCMP heavy atom derivative superimposed. Five density peaks appear about the fivefold icosahedral axes, but only three about the quasi sixfold axes, as the mercury atoms are bound by Cys126 of only the A and B subunits.