Project description:The oldest authenticated peptide sequences to date were reported in 2016 from 3.8 Ma old ostrich eggshell (OES) from the site of Laetoli, Tanzania (Demarchi et al., 2016). Here we demonstrate survival of the same sequences in 6.5-9Ma OES recovered from a palaeosteppe setting in northwestern China. The eggshell is thicker than those observed in extant species and consistent with the Liushu Struthio sp. ootaxon. These findings push the preservation of ancient proteins back to the Miocene and highlight their potential for paleontology, paleoecology and evolutionary biology.
Project description:Claims for exceptional preservation of biomolecules in the fossil record are contested. Here we demonstrate the role of surface stabilisation in significantly prolonging protein sequence survival to ~3.8 million years. The intracrystalline environment of calcite ostrich (Struthionidae) eggshell encapsulates uterine proteins and molecular dynamics simulations of struthiocalcin-1 & -2, the dominant proteins within the eggshell, reveal that they bind to the mineral surface in distinct domains. By ~3.8 million years the struthiocalcin-1 domain with the lowest calculated binding energy is selectively preserved in eggshell samples from equatorial Africa. Sequence survival is explained by entropy loss of the peptide and water, lowering the effective temperature of the local environment at the peptide mineral interface.
