The Archaeal Proteome Project advances knowledge about archaeal cell biology through comprehensive proteomics

Modern proteomics approaches can explore whole proteomes within a single mass spectrometry (MS) run. However, the enormous amount of MS data generated often remains incompletely analyzed due to a lack of sophisticated bioinformatic tools and expertise needed from a diverse array of fields. In particular, in the field of microbiology, efforts to combine large-scale proteomic datasets have so far largely been missing. Thus, despite their relatively small genomes, the proteomes of most archaea remain incompletely characterized. This in turn undermines our ability to gain a greater understanding of archaeal cell biology.

Therefore, we have initiated the Archaeal Proteome Project (ArcPP), a community effort that works towards a comprehensive analysis of archaeal proteomes. Starting with the model archaeon Haloferax volcanii, using state-of-the-art bioinformatic tools, we have:

• reanalyzed more than 23 Mio. spectra
• optimized the analysis using parameter sweeps, multiple search engines implemented in Ursgal, and the combination of resultsthrough the combined PEP approach
• thoroughly controlled false discovery rates for high confidence protein identifications using the picked protein FDR approach and limiting FDR to 0.5%
• identified more than 40k peptides, corresponding to 2930 proteins (>72% of the proteome) with a median sequence coverage of 51%.

Benefiting from the established bioinformatic infrastructure, we will follow up on this analysis focusing on H. volcanii proteogenomics as well as the characterization of various post-translational modifications. Furthermore, ArcPP will integrate quantitative results obtained from the individual datasets in order to identify common regulatory mechanisms. These studies on the H. volcanii proteome can serve as a blueprint for comprehensive proteomic analyses performed on a diverse range of archaea and bacteria.