Mapping phosphoproteins in Mycoplasma genitalium and Mycoplasma pneumoniae

We identified a total of 24 distinct phosphoproteins, about 3% and 5% of the total protein complement in M. pneumoniae and M. genitalium, respectively, indicating that phosphorylation occurs with prevalence similar to many other bacterial species. Identified phosphoproteins include pyruvate dehydrogenase E1 alpha and beta subunits, enolase, heat shock proteins DnaK and GroEL, elongation factor Tu, cytadherence accessory protein HMW3, P65, and several hypothetical proteins. These proteins are involved in energy metabolism, carbohydrate metabolism, translation/transcription and cytadherence. Interestingly, fourteen of the 24 phosphoproteins we identified (58%) were previously reported as putatively associated with a cytoskeleton-like structure that is present in the mycoplasmas, indicating a potential regulatory role for phosphorylation in this structure.This study has shown that phosphorylation in mycoplasmas is comparable to that of other bacterial species. Our evidence supports a link between phosphorylation and cytadherence and/or a cytoskeleton-like structure, since over half of the proteins identified as phosphorylated have been previously associated with these functions. This opens the door to further research into the purposes and mechanisms of phosphorylation for mycoplasmas.Post-translational modification of proteins is known to be a critical part of many biological pathways, yet in the mycoplasma species, little is known about the extent of protein modification that occurs. Mycoplasmas are wall-less prokaryotes and primarily mucosal pathogens of respiratory or urogenital tracts [1]. Mycoplasma genitalium has the smallest genome (580,070 bp) known for a free-living organism, with its close relative Mycoplasma pneumoniae having a larger genome (816,394 bp) that contains orthologs of all of the M. genitalium genes plus approximately 200 additional genes [2-4]. While only a few occurrences of phosphorylation, lipid modification, and proteolytic processing of pr