An interstitial peptide is readily processed from within seed proteins

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• De novo protein evolution is crucial, but often involves coding transcripts from non-coding DNA.
• The SunFlower Trypsin Inhibitor 1 (SFTI-1) peptide macrocycle evolved from a precursor protein region over millions of years.
• SFTI-1 and its precursor albumin are processed by asparaginyl endopeptidase (AEP).

Purpose of the Study:

• To investigate if SFTI-1's evolution within a latent precursor region was essential.
• To explore alternative origins and processing mechanisms for de novo peptide evolution.

Main Methods:

• Transgene approach in Arabidopsis thaliana.
• Peptide mass spectrometry analysis.
• Reverse transcription quantitative PCR (RT-qPCR).

Main Results:

• SFTI-1 can emerge from alternative locations within preproalbumin.
• SFTI-1 can be precisely processed from unrelated seed proteins via AEP.
• SFTI-1 production decreased significantly without the adjacent albumin.

Conclusions:

• The genetic expansion for SFTI-1 did not critically require a latent protein region.
• Interstitial peptides evolving within existing proteins may be widespread.
• SFTI-1 exemplifies de novo functional peptide evolution without a new gene.