Functional annotation of Pseudomonas aeruginosa membrane proteins in response to micronutrients

The opportunistic pathogen Pseudomonas aeruginosa PAO1 is well known for its environmental and metabolic versatility, and large genome of 6.3Mbp. Studying the proteome is key to providing accurate, and informative genome annotation. Past studies of the proteome of P. aeruginosa have provided proteomic profiles and information supportive for the existence of hypothetical proteins, but many have failed to provide anything more, and so functional annotation has lagged behind. In this study, 2000 non-redundant proteins from membrane and soluble fractions of PAO1 were quantifiably identified using a targeted proteomics approach after growth with the addition of copper or cobalamin to the growth medium. From this, eight differentially expressed but poorly annotated proteins were chosen for further functional annotation work. A knockout study was performed using transposon insertion mutants of the genes for the eight candidate proteins and growth assays were performed to provide support for their putative functions. A highlight from this group was candidate protein PA3920, which was identified in this study as a PtypeATPase for Cu²⁺. This work jointly provides evidence for the function of a number of putative proteins and acts as a stepping-stone for further annotation work with the large list of proteins identified.