title: Penicillin-binding protein SpoVD disulphide is a target for StoA in Bacillus subtilis forespores.
abstract: The bacterial endospore is a dormant and heat-resistant form of life. StoA (SpoIVH) in Bacillus subtilis is a membrane-bound thioredoxin-like protein involved in endospore cortex synthesis. It is proposed to reduce disulphide bonds in hitherto unknown proteins in the intermembrane compartment of developing forespores. Starting with a bioinformatic analysis combined with mutant studies we identified the sporulation-specific, high-molecular-weight, class B penicillin-binding protein SpoVD as a putative target for StoA. We then demonstrate that SpoVD is a membrane-bound protein with two exposed redox-active cysteine residues. Structural modelling of SpoVD, based on the well characterized orthologue PBP2x of Streptococcus pneumoniae, confirmed that a disulphide bond can form close to the active site of the penicillin-binding domain restricting access of enzyme substrate or functional association with other cortex biogenic proteins. Finally, by exploiting combinations of mutations in the spoVD, stoA and ccdA genes in B. subtilis cells, we present strong in vivo evidence that supports the conclusion that StoA functions to specifically break the disulphide bond in the SpoVD protein in the forespore envelope. The findings contribute to our understanding of endospore biogenesis and open a new angle to regulation of cell wall synthesis and penicillin-binding protein activity.
authors.affiliation: Department of Cell & Organism Biology, Lund University, Lund, Sweden.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Liu
authors.forename: Mirja
authors.initials: M
authors.lastname: Carlsson Möller
authors.forename: Lise
authors.initials: L
authors.lastname: Petersen
authors.forename: Christopher A G
authors.initials: CA
authors.lastname: Söderberg
authors.forename: Lars
authors.initials: L
authors.lastname: Hederstedt
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D004220:Disulfides / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D046915:Penicillin-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013171:Spores, Bacterial / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D026901:Membrane Transport Proteins; D046915:Penicillin-Binding Proteins; C085450:SpoVD protein, Bacillus subtilis; C072223:PBP 2x protein, Streptococcus; D019704:Protein Disulfide-Isomerases