| Comments |
P.343 left column: "Independent of the precise genetic mechanism involved, combining ancestral protein domains that were originally separate is apparently the basic principle by which many polypeptides with new functions evolved. This process has occurred with much higher frequency in eukaryotes than in prokaryotes, as is evident from a simple comparison of prokaryotic and eukaryotic protein structures using the information recently provided by several genome projects (Fig. 1). Although the size distribution of protein domains is uniform throughout the kingdoms of life (ref 2), eukaryotes contain a much greater number (and proportion) of longer polypeptides combining multiple domains." |