Abstract
Mycoplasma pneumoniae is a significant cause of pneumonia and post infection sequelae affecting organ sites distant to the respiratory tract are common. It is also a model organism where extensive ‘omics’ studies have been conducted to gain insight into how minimal genome self-replicating organisms function. An N-terminome study undertaken here identified 4898 unique N-terminal peptides that mapped to 391 (56%) predicted M. pneumoniae proteins. True N-terminal sequences beginning with the initiating methionine (iMet) residue from the predicted Open Reading Frame (ORF) were identified for 163 proteins. Notably, almost half (317; 46%) of the ORFS derived from M. pneumoniae strain M129 are post-translationally modified, presumably by proteolytic processing, because dimethyl labelled neo-N-termini were characterised that mapped beyond the predicted N-terminus. An analysis of the N-terminome describes endoproteolytic processing events predominately targeting tryptic-like sites, though cleavages at negatively charged residues in P1′ (D and E) with lysine or serine/alanine in P2′ and P3′ positions also occurred frequently. Surfaceome studies identified 160 proteins (23% of the proteome) to be exposed on the extracellular surface of M. pneumoniae. The two orthogonal methodologies used to characterise the surfaceome each identified the same 116 proteins, a 72% (116/160) overlap. Apart from lipoproteins, transporters, and adhesins, 93/160 (58%) of the surface proteins lack signal peptides and have well characterised, canonical functions in the cell. Of the 160 surface proteins identified, 134 were also targets of endo-proteolytic processing. These processing events are likely to have profound implications for how the host immune system recognises and responds to M. pneumoniae.
Highlights
We recently analyzed the N-terminome and surfaceome of the porcine respiratory pathogen Mycoplasma hyopneumoniae[20], an organism significant for its role as a cause of major economic loss and as a driver of antimicrobial use in pig production[21]
It is notable that while M. pneumoniae has been the subject of intensive study as a model minimal genome bacterium, there have been no systematic analyses of proteolytic protein processing, nor studies that have sought to define the comprehensive repertoire of surface proteins of this important human pathogen
Analysis of the N-termini mapping to positions 1 and 2 of their respective open reading frame (ORF) demonstrated that classical N-end rules[23] apply in M. pneumoniae (Fig. 1A; Supplementary Data 1); with the identification of 163 M. pneumoniae proteins beginning with the predicted initiating methionine residue
Summary
We recently analyzed the N-terminome and surfaceome of the porcine respiratory pathogen Mycoplasma hyopneumoniae[20], an organism significant for its role as a cause of major economic loss and as a driver of antimicrobial use in pig production[21]. It is notable that while M. pneumoniae has been the subject of intensive study as a model minimal genome bacterium, there have been no systematic analyses of proteolytic protein processing, nor studies that have sought to define the comprehensive repertoire of surface proteins of this important human pathogen. We provide an in-depth analysis of two cleaved M. pneumoniae surface proteins (MPN052; MPN674); in one instance (MPN674) cleavage fragments retained binding affinities of the parent molecule, while in the other, the fragments gained binding affinities absent in the parent molecule. These observations have significant ramifications for defining the functional proteome of M. pneumoniae, understanding pathogenesis and informing subunit vaccine design
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
