Protein Folds Research Offers Insight into Metabolic Evolution
This article describes how researchers at the University of Illinois have created a phylogenetic tree (family tree) that tracks the evolution of proteins. They formed the tree on the assumption that protein folds (areas of activity) that were used by the most species were the oldest. They looked at 776 protein folds used by 200 different species of bacteria, archaea, protists, animals, plants, and fungi. 16 of the folds found were universal across all species, and nine of these evolved around the time of the earliest divergences of species. The researchers wrote that “These nine ancient folds represent architectures of fundamental importance undisputedly encoded in a genetic core that can be traced back to the universal ancestor of the three super kingdoms of life.”
What makes these results exciting is that the nine oldest folds are involved in RNA metabolism. The current hypothesis about the origins of life states that life was originally RNA based, and that self-splicing RNA both carried genetic material (from which it could make proteins) and had metabolic function (that enabled it to make proteins-important because DNA requires the use of proteins to transcribe genes). If the oldest proteins do contain RNA activity, then the earliest life most likely was RNA based.