Molecular evolution before the origin of species

Area of Science:

• Biochemistry
• Evolutionary Biology
• Molecular Biology

Background:

• Amino acid residue profiles in ancient proteins can indicate their evolutionary timeline.
• The order of amino acid addition to the genetic code is supported by molecular evidence and biosynthesis pathways.

Purpose of the Study:

• To determine the origin times of amino acids and proteins by analyzing conserved residues in ancient protein sequences.
• To correlate protein evolution with the historical development of the genetic code.

Main Methods:

• Phylogenetic analysis of 844 diverse protein sequences from 10 ancient proteins.
• Evaluation of 'code age' for residue profiles based on biosynthesis path length and molecular evidence.
• Comparison of origin estimates for conserved versus non-conserved amino acid residues.

Main Results:

• Conserved residues yielded significantly earlier origin estimates than non-conserved ones, corroborating the biosynthetic order of amino acid addition.
• Low potential ferredoxin (Fdxn) exhibited the earliest residue profile, suggesting a role in primordial surface systems before cell formation.
• Proteolipid (PL) helix-1 and cell division protein FtsZ (FtsZ) profiles indicate later evolution, correlating with early cell membrane and division mechanisms.

Conclusions:

• Primary protein structure analysis supports the biosynthetic timeline of amino acid incorporation into the genetic code.
• Early proteins, like Fdxn, likely anchored cofactors to mineral surfaces, a general pre-cell protein function.
• The evolution of proteins with hydrophobic domains, like PL, was crucial for cell membrane formation and subsequent DNA genome development.