Beatrice Demarchi

Protein survival: deep time?

Beatrice Demarchi§

§ Department of Life Sciences and Systems Biology, University of Turin, Italy

The role of palaeoproteomics in answering a range of archaeological questions is undeniable, and has become even more prominent in the past few years. It is well known that proteins are more resistant to diagenesis than DNA, and this makes them an ideal substrate for developing molecular approaches in palaeoanthropology and paleontology. However, the time span of the applicability of the technique is still uncertain: degradation primarily depends on the combined effect of time and temperature and, in systems that are not closed, on the physical and chemical characteristics of the burial environment. Currently, the oldest authenticated peptide sequence is that isolated from the intra-crystalline organic fraction within ostrich eggshell from 2-3.8 Ma sites in Africa (Laetoli, Olduvai Gorge; thermal age ~16Ma@10℃). While it is likely that older peptides and proteins will soon be discovered and reported, this substrate has offered one of the few opportunities for a mechanistic study of protein preservation.

Here we present a range of palaeoproteomics data obtained on eggshell and other biominerals from sites in Africa and India, in order to explore some of the patterns of diagenesis and survival of ancient peptides in fossils from warm environments. We specifically discuss the impact of mineral binding, which increases the energy barrier for peptide bond hydrolysis. Although the rate of hydrolysis is slowed down, it does eventually occur, and thus the potential for phylogenetic study dwindles.