Architecture of Limulus polyphemus Hemocyanin

" The architecture of the 48-meric hemocyanin of the horseshoe crab Limulus polyphemus has been determined from electron micrographs of whole(48-mer) molecules and half-(24mer) molecules.The assembly of hexamers of kidney-shaped subunits can produce two dodecameric enantiomorphs,designated as right and left.The assembly of 24-mers can again result in two enantiomorphs.By taking into account the rocking effect described by Van Heel and Frank[Van Heel,M.,& Frank,J.(1981)Ultramicroscopy 6,187-194],we deduced that the 24-meric half-molecule is made up of two copies of the left dodecameric enantiomorph.In addition,the two constituent dodecamers of the half-molecule are shifted with respect to a symmetric head-to-tail arrangement,which makes it possible to distinguish two different faces of the 24-mer,termed flip and flop.A model of the whole molecule."