期刊
MOLECULAR BIOLOGY AND EVOLUTION
卷 34, 期 6, 页码 1505-1516出版社
OXFORD UNIV PRESS
DOI: 10.1093/molbev/msx104
关键词
Asteraceae; biosynthesis; peptide; sunflower; protein evolution
资金
- Australian Research Council (ARC) Discovery Project [DP130101191]
- ARC Super Science Fellowship [FS100100022]
- ARC Future Fellowships [FT130100123, FT120100013]
- ARC Centre of Excellence grant [CE140100008]
- ARC [DP120103369]
- Australian Postgraduate Award
- International Postgraduate Research Scholarship
- Betty Green Postgraduate Research Scholarship
- Australian Research Council [FT130100123] Funding Source: Australian Research Council
The de novo evolution of genes and the novel proteins they encode has stimulated much interest in the contribution such innovations make to the diversity of life. Most research on this de novo evolution focuses on transcripts, so studies on the biochemical steps that can enable completely new proteins to evolve and the time required to do so have been lacking. Sunflower Preproalbumin with SFTI-1 (PawS1) is an unusual albumin precursor because in addition to producing albumin it also yields a potent, bicyclic protease-inhibitor called SunFlower Trypsin Inhibitor-1 (SFTI-1). Here, we show how this inhibitor peptide evolved stepwise over tens of millions of years. To trace the origin of the inhibitor peptide SFTI-1, we assembled seed transcriptomes for 110 sunflower relatives whose evolution could be resolved by a chronogram, which allowed dates to be estimated for the various stages of molecular evolution. A genetic insertion event in an albumin precursor gene similar to 45 Ma introduced two additional cleavage sites for protein maturation and conferred duality upon PawS1-Like genes such that they also encode a small buried macrocycle. Expansion of this region, including two Cys residues, enlarged the peptide similar to 34 Ma and made the buried peptides bicyclic. Functional specialization into a protease inhibitor occurred similar to 23 Ma. These findings document the evolution of a novel peptide inside a benign region of a pre-existing protein. We illustrate how a novel peptide can evolve without de novo gene evolution and, critically, without affecting the function of what becomes the protein host.
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