Elucidating the Native Topologies of Bacterial Microcompartments

Bacterial microcompartments, or MCPs, are supramolecular structures analogous to eukaryotic organelles. These assemblies are understood to organize and compartmentalize the cytosol by sequestering and optimizing a myriad of metabolic reactions. They enable the diffusive transport of substrates, acting as a semi-permeable barrier that prevents the efflux of toxic intermediates. Unlike their membrane-bound eukaryotic counterparts, MCPs are comprised entirely of a proteinaceous outer shell. The so-called BMC domain (for bacterial microcompartment) is the canonical building block for all MCPs. BMCs oligomerize to form hexamers disks which tesselate laterally to form the nearly flat facets of the outer MCP shell. Pentameric proteins form the polyhedral vertices. Despite persistent research in the field, bacterial microcompartments remain poorly understood. This work seeks to enhance our foundational knowledge of MCPs through structurally characterizing BMS shell proteins and highlighting their potentially specialized functions, presenting a novel structural resource that organizes existing structural data and recent work that begins to reveal the native topology and long-range organization of MCP shells