3ERW

Crystal Structure of StoA from Bacillus subtilis

Summary for 3ERW

• Entry DOI: 10.2210/pdb3erw/pdb
• Descriptor: Sporulation thiol-disulfide oxidoreductase A (2 entities in total)
• Functional Keywords: thioredoxin-like fold, resa-like fold, disulfide, dithiol, stoa, oxidoreductase, redox-active center, sporulation
• Biological source: Bacillus subtilis
• Cellular location: Spore wall, spore outer membrane (Probable): O31687
• Total number of polymer chains: 7
• Total formula weight: 115439.46

Authors

Crow, A.,Liu, Y.,Moller, M.C.,Le Brun, N.E.,Hederstedt, L. (deposition date: 2008-10-03, release date: 2009-01-20, Last modification date: 2024-10-09)

Primary citation

Crow, A.,Liu, Y.,Moller, M.C.,Le Brun, N.E.,Hederstedt, L.
Structure and Functional Properties of Bacillus subtilis Endospore Biogenesis Factor StoA
J.Biol.Chem., 284:10056-10066, 2009

PubMed Abstract: Bacillus subtilis StoA is an extracytoplasmic thiol-disulfide oxidoreductase (TDOR) important for the synthesis of the endospore peptidoglycan cortex protective layer. Here we demonstrate that StoA is membrane-associated in B. subtilis and report the crystal structure of the soluble protein lacking its membrane anchor. This showed that StoA adopts a thioredoxin-like fold with N-terminal and internal additions that are characteristic of extracytoplasmic TDORs. The CXXC active site of the crystallized protein was found to be in a mixture of oxidized and reduced states, illustrating that there is little conformational variation between redox states. The midpoint reduction potential was determined as -248 mV versus normal hydrogen electrode at pH 7 consistent with StoA fulfilling a reductive role in endospore biogenesis. pK(a) values of the active site cysteines, Cys-65 and Cys-68, were determined to be 5.5 and 7.8. Although Cys-68 is buried within the structure, both cysteines were found to be accessible to cysteine-specific alkylating reagents. In vivo studies of site-directed variants of StoA revealed that the active site cysteines are functionally important, as is Glu-71, which lies close to the active site and is conserved in many reducing extracytoplasmic TDORs. The structure and biophysical properties of StoA are very similar to those of ResA, a B. subtilis extracytoplasmic TDOR involved in cytochrome c maturation, raising important general questions about how these similar but non-redundant proteins achieve specificity. A detailed comparison of the two proteins demonstrates that relatively subtle differences, largely located around the active sites of the proteins, are sufficient to confer specificity.

PubMed: 19144642
DOI: 10.1074/jbc.M809566200

Experimental method

X-RAY DIFFRACTION (2.5 Å)