The primitive code and repeats of base oligomers as the primordial protein-encoding sequence

Area of Science:

• Origin of Life Research
• Molecular Evolution
• Biochemistry

Background:

• The spontaneous generation of life faces challenges with early translational machinery.
• Primitive translation systems might have struggled with non-preselected base sequences.
• Early genetic codes, like the primitive mitochondria-like code, could hinder the production of long polypeptides.

Purpose of the Study:

• To propose a mechanism for the origin of life overcoming early translation limitations.
• To identify early genetic sequences that could produce functional polypeptides.
• To investigate the role of oligonucleotide repeats in early protein synthesis.

Main Methods:

• Analysis of a mouse transcript containing conserved tetranucleotide repeats.
• In silico translation of the repeat sequence using a primitive mitochondria-like code.
• Examination of the resulting polypeptide chain lengths and periodicities.

Main Results:

• A mouse transcript with conserved tetranucleotide repeats was identified.
• Translation of this transcript, even with a primitive code, yielded long polypeptides (245-251 residues).
• These polypeptides exhibited periodical structures and acquired longer periodicities, suggesting secondary structure formation.

Conclusions:

• Oligonucleotide repeats likely formed the first translated base sequences in early life.
• These sequences facilitated the rapid acquisition of longer periodicities and secondary structures (alpha-helical, beta-sheet).
• This provides a plausible pathway for the emergence of functional polypeptides crucial for life's origin.