期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：17
页码：6385-6390
DOI：10.1073/pnas.0307709101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Bacillus subtilis is a bacterium that undergoes a developmental program of sporulation in response to starvation. At the core of the program are {sigma} factors, whose regulated spatiotemporal activation controls much of the gene expression. Activation of pro-{sigma}K in the mother cell compartment involves regulated intramembrane proteolysis (RIP) in response to a signal from the forespore. RIP is a poorly understood process that is conserved in prokaryotes and eukaryotes. Here, we report a powerful system for studying RIP of pro-{sigma}K. Escherichia coli was engineered to coexpress the putative membrane-embedded metalloprotease SpoIVFB with pro-{sigma}K and potential inhibitors of RIP. Overproduction of SpoIVFB and pro-{sigma}K in E. coli allowed accurate and abundant proteolytic processing of pro-{sigma}K with the characteristics expected for SpoIVFB acting as an intramembrane-cleaving protease (I-Clip). Coexpression of BofA in this system led to formation of a BofA-SpoIVFB complex and marked inhibition of pro-{sigma}K processing. Mutational analysis identified amino acids in BofA that are necessary for complex formation and inhibition of processing, leading us to propose that BofA inhibits SpoIVFB metalloprotease activity by providing a metal ligand, analogous to the cysteine switch mechanism of matrix metalloprotease regulation. The approach described herein should be applicable to studies of other RIP events and amenable to developing in vitro assays for I-Clips.
