We report a sequence reconstruction analysis targeting several Precambrian nodes in the evolution of class-A β-lactamases and the preparation and experimental characterization of their encoded proteins. Despite extensive sequence differences with the modern enzymes (~100 amino acid differences), the proteins resurrected in the laboratory properly fold into the canonical lactamase structure. The...

55Swain, F. M., A Blumentals, and N. Prokopovich, "Bituminous and other organic substances in Pre-Cambrian of Minnesota," Am. Assoc. Petrol. Geol. Bull., 42, 173-189 (1958). M Timofeev, B. V., "Spores and phytoplankton from Proterozoic and early Paleozoic of Eurasia," in Proc. 21st Int. Geol. Congr., Copenhagen, Rept. Soviet Geologists, Problem 9, 177-188 (1960) (in Russian; English abstract, p...

The earliest evidence for animal life comes from the fossil record of 24-isopropylcholestane, a sterane found in Cryogenian deposits, and whose precursors are found in modern demosponges, but not choanoflagellates, calcareans, hexactinellids, or eumetazoans. However, many modern demosponges are also characterized by the presence of siliceous spicules, and there are no convincing demosponge spic...