Protein sequences bound to mineral surfaces persist into deep time

Area of Science:

• Paleoproteomics
• Biomineralization
• Paleontology

Background:

• Proteins are more durable than DNA in the fossil record, but their preservation mechanisms and longevity are debated.
• Ostrich eggshells contain abundant structural proteins like struthiocalcin-1 and -2, making them ideal for studying protein preservation.

Purpose of the Study:

• To investigate the role of mineral binding in preserving protein sequences within ancient ostrich eggshell fossils.
• To establish the authenticity and age of preserved protein sequences from paleontological sites.

Main Methods:

• Analysis of protein diagenesis in ostrich eggshell from Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma).
• Molecular dynamics simulations to model the binding of struthiocalcin-1 and -2 to calcite surfaces.
• Thermal age calculations to estimate the age of preserved peptides.

Main Results:

• Consistent patterns of protein preservation were observed, supporting the authenticity of the sequences.
• Molecular dynamics simulations identified specific protein domains with strong binding affinities to the mineral surface.
• The domain with the highest calculated binding energy to calcite was selectively preserved.
• Peptides from Laetoli and Olduvai Gorge were found to be approximately 50 times older than previously authenticated sequences, equivalent to ~16 million years.

Conclusions:

• Mineral binding is a critical mechanism for preserving protein sequences in the fossil record.
• The selective preservation of strongly bound protein domains explains their longevity.
• This study significantly extends the age range of authenticated fossil protein sequences, opening new avenues for paleoproteomic research.