4c2f
Crystal structure of the CtpB R168A mutant present in an active conformation
Structural highlights
FunctionCTPB_BACSU Involved in the signal transduction pathway leading to the proteolytic activation of the mother cell transcription factor pro-sigma-K during sporulation. The signaling serine protease CtpB triggers pro-sigma-K processing by cleaving the regulatory protein SpoIVFA and is necessary for the proper timing of sigma-K activation.[1] [2] [3] Publication Abstract from PubMedSpore formation in Bacillus subtilis relies on a regulated intramembrane proteolysis (RIP) pathway that synchronizes mother-cell and forespore development. To address the molecular basis of this SpoIV transmembrane signaling, we carried out a structure-function analysis of the activating protease CtpB. Crystal structures reflecting distinct functional states show that CtpB constitutes a ring-like protein scaffold penetrated by two narrow tunnels. Access to the proteolytic sites sequestered within these tunnels is controlled by PDZ domains that rearrange upon substrate binding. Accordingly, CtpB resembles a minimal version of a self-compartmentalizing protease regulated by a unique allosteric mechanism. Moreover, biochemical analysis of the PDZ-gated channel combined with sporulation assays reveal that activation of the SpoIV RIP pathway is induced by the concerted activity of CtpB and a second signaling protease, SpoIVB. This proteolytic mechanism is of broad relevance for cell-cell communication, illustrating how distinct signaling pathways can be integrated into a single RIP module. CtpB Assembles a Gated Protease Tunnel Regulating Cell-Cell Signaling during Spore Formation in Bacillus subtilis.,Mastny M, Heuck A, Kurzbauer R, Heiduk A, Boisguerin P, Volkmer R, Ehrmann M, Rodrigues CD, Rudner DZ, Clausen T Cell. 2013 Oct 24;155(3):647-58. doi: 10.1016/j.cell.2013.09.050. Epub 2013 Oct, 24. PMID:24243021[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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