Comparison of the complete protein sets of worm and yeast: Orthology and divergence

Comparative analysis of predicted protein sequences encoded by the genomes of Caenorhabditis elegans and Saccharomyces cerevisiae suggests that most o f the core biological functions are carried out by orthologous proteins (pr oteins of different species that can be traced back to a common ancestor) t hat occur in comparable numbers. The specialized processes of signal transd uction and regulatory control that are unique to the multicellular worm app ear to use novel proteins, many of which re-use conserved domains. Major ex pansion of the number of some of these domains seen in the worm may have co ntributed to the advent of multicellularity, The proteins conserved in yeas t and worm are Likely to have orthologs throughout eukaryotes; in contrast, the proteins unique to the worm may well define metazoans.