N-terminomics identifies widespread endoproteolysis and novel methionine excision in a genome-reduced bacterial pathogen

• Published in: Scientific reports 2017-09, Vol.7 (1), p.11063-17, Article 11063
• Main Authors: Berry, Iain J., Jarocki, Veronica M., Tacchi, Jessica L., Raymond, Benjamin B. A., Widjaja, Michael, Padula, Matthew P., Djordjevic, Steven P.
• Format: Article
• Language: English
• Subjects: 631/326/421; 631/45/475; 82/16; 82/58; 82/81; 82/83; Actin; Affinity; Affinity chromatography; Arginine; Baits; Cell surface; Fibronectin; Genomes; Glyceraldehyde; Glyceraldehyde 3-phosphate; Glyceraldehyde-3-phosphate dehydrogenase; Heparin; Humanities and Social Sciences; Methionine; multidisciplinary; Pathogens; Peptides; Proteins; Proteolysis; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-11296-9

Proteolytic processing alters protein function. Here we present the first systems-wide analysis of endoproteolysis in the genome-reduced pathogen Mycoplasma hyopneumoniae . 669 N-terminal peptides from 164 proteins were identified, demonstrating that functionally diverse proteins are processed, more than half of which 75 (53%) were accessible on the cell surface. Multiple cleavage sites were characterised, but cleavage with arginine in P1 predominated. Putative functions for a subset of cleaved fragments were assigned by affinity chromatography using heparin, actin, plasminogen and fibronectin as bait. Binding affinity was correlated with the number of cleavages in a protein, indicating that novel binding motifs are exposed, and protein disorder increases, after a cleavage event. Glyceraldehyde 3-phosphate dehydrogenase was used as a model protein to demonstrate this. We define the rules governing methionine excision, show that several aminopeptidases are involved, and propose that through processing, genome-reduced organisms can expand protein function.