Using QconCATs to establish protein complex stoichiometry

Mengru Yang, Deborah M Simpson, Nicolas Wenner, Philip Brownridge, Victoria M Harman, Jay C D Hinton, Robert J Beynon, Lu-Ning Liu (2020) Decoding the stoichiometric composition and organisation of bacterial metabolosomes Nat Commun 11(1):1976. doi: 10.1038/s41467-020-15888-4.

Some enteric bacteria including Salmonella have evolved the propanediol-utilising microcompartment (Pdu MCP), a specialised proteinaceous organelle that is essential for 1,2-propanediol degradation and enteric pathogenesis. Pdu MCPs are a family of bacterial microcompartments that are self-assembled from hundreds of proteins within the bacterial cytosol. Here, we seek a comprehensive understanding of the stoichiometric composition and organisation of Pdu MCPs. We obtain accurate stoichiometry of shell proteins and internal enzymes of the natural Pdu MCP by QconCAT-driven quantitative mass spectrometry. Genetic deletion of the major shell protein and absolute quantification reveal the stoichiometric and structural remodelling of metabolically functional Pdu MCPs. Decoding the precise protein stoichiometry allows us to develop an organisational model of the Pdu metabolosome. The structural insights into the Pdu MCP are critical for both delineating the general principles underlying bacterial organelle formation, structural robustness and function, and repurposing natural microcompartments using synthetic biology for biotechnological applications.