Within orthogroups, the average molecular weight (MW) of extracellular homomers is smaller than the MW of cytoplasmic monomers, but there is no difference in their subunits (one-sample Wilcoxon-tests). This suggests that besides CNE, the selection also shapes their quaternary structure. Note that due to the larger size of eukaryotic proteins, prokaryotes and eukaryotes were treated separately, even within orthogroups.
