A versatile nano display platform from bacterial spore coat proteins

Abstract

Dormant bacterial spores are encased in a thick protein shell, the “coat”, which contains ~70 different proteins. The coat protects the spore from environmental insults, and is among the most durable static structures in biology. Due to extensive cross-linking among coat proteins, this structure has been recalcitrant to detailed biochemical analysis, so molecular details of how it assembles are largely unknown. Here, we reconstitute the basement layer of the coat atop spherical membranes supported by silica beads to create artificial spore-like particles. We report that these synthetic spore husk-encased lipid bilayers (SSHELs) assemble and polymerize into a static structure, mimicking in vivo basement layer assembly during sporulation in Bacillus subtilis. Additionally, we demonstrate that SSHELs may be easily covalently modified with small molecules and proteins. We propose that SSHELs may be versatile display platforms for drugs and vaccines in clinical settings, or for enzymes that neutralize pollutants for environmental remediation.

Cell Death Pathway That Monitors Spore Morphogenesis

“…In contrast to the early-acting sporulation checkpoint pathways described above, this pathway monitors the assembly of the spore envelope, which occurs late in the sporulation program. In B. subtilis , the basement layer of the spore coat contains SpoVM , a 26 aa protein (35) that preferentially localizes to the positively curved membrane surrounding the forespore to mark it as the site for coat assembly (36–38); and SpoIVA , an unusual ATPase derived from a family of GTPases which harnesses the energy from ATP hydrolysis to drive its irreversible polymerization into a static platform atop which the rest of the spore coat assembles (39–42). Mutations in spoVM or spoIVA , but not the ~80 other coat proteins (43–45), result not only in defective coat formation but also failure to initiate cortex assembly, suggesting that the assemblies of the coat and cortex are somehow coordinated by SpoVM and SpoIVA (46, 47).…”

Dash-and-Recruit Mechanism Drives Membrane Curvature Recognition by the Small Bacterial Protein SpoVM

“…Additionally, when incubated with a population of giant unilamellar vesicles of mixed sizes composed of phosphatidylcholine, purified SpoVM preferentially adsorbed onto the most convex vesicles available (Ramamurthi et al, 2009). After adsorption, SpoVM recruits a structural protein, SpoIVA (Ramamurthi et al, 2006; Roels et al, 1992), which hydrolyzes ATP to irreversibly polymerize into a platform encasing the forespore on top of which the rest of the coat assembles (Castaing et al, 2013; Ramamurthi and Losick, 2008; Wu et al, 2015). SpoVM mislocalization not only prevents the proper assembly of this basement layer, but also the rest of the spore coat (Ramamurthi et al, 2006).…”

A Quality-Control Mechanism Removes Unfit Cells from a Population of Sporulating Bacteria

“…SpoVM recruits the structural protein SpoIVA (Price and Losick, 1999; Ramamurthi et al, 2006; Roels et al, 1992; Wu et al, 2015) which polymerizes irreversibly in an ATP-dependent manner around the forespore surface (Castaing et al, 2013; Ramamurthi and Losick, 2008). Deletion of either spoVM or spoIVA results in a misassembled coat that is not anchored to the forespore surface (Levin et al, 1993; Roels et al, 1992).…”