Figure 6.

A hypothetical model for the evolution of CDGSH proteins. The occurrence of Class I and Class II CDGSH proteins is shown in major lineages from the 3 domains of life. Bacteria are shown to primarily contain Class II CDGSH proteins, whereas archaea and eukaryotes contain Class I and Class II CDGSH proteins. Eukaryote Class II CDGSH proteins are proposed to have originated from the endosymbayotic event that yielded the mitochondria. Class I CDGSH proteins are postulated to have evolved only after archaea and eukaryotes have radiated from bacteria. LUCA, last universal common ancestor, LACA, last archaeal common ancestor, LECA, last eukaryote common ancestor, LBCA, last bacterial common ancestor.