Related Experiment Video
Updated: Jul 10, 2026

Assaying Proteasomal Degradation in a Cell-free System in Plants
Published on: March 27, 2014
A branched pathway governing the activation of a developmental transcription factor by regulated intramembrane
Nathalie Campo1, David Z Rudner
1Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts 02115, USA.
Abstract:
The proteolytic activation of the membrane-associated transcription factor pro-sigma(K) is controlled by a signal transduction pathway during sporulation in the bacterium Bacillus subtilis. The pro-sigma(K) processing enzyme SpoIVFB, a membrane-embedded metalloprotease, is held inactive by two other integral-membrane proteins, SpoIVFA and BofA. We demonstrate that the signaling protease SpoIVB (IVB) triggers pro-sigma(K) processing by cleaving the extracellular domain of the SpoIVFA regulator at multiple sites. In vitro, these cleavages do not disrupt the interactions between SpoIVFA, SpoIVFB, and BofA, suggesting that IVB-dependent activation of the processing enzyme results from a conformational change in this complex. Our data further suggest that when IVB is unable to cleave SpoIVFA, it can still activate pro-sigma(K) processing through a second protease, CtpB. Finally, we demonstrate that CtpB, like IVB, triggers pro-sigma(K) processing by cleaving SpoIVFA. We propose that IVB regulates intramembrane proteolysis through two proteolytic pathways, both of which converge on the same regulator.
Related Concept Videos
Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
The Intrinsic Apoptotic Pathway
Interactions Between Signaling Pathways
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
Amplifying Signals via Enzymatic Cascade
MAPK Signaling Cascades
TGF - β Signaling Pathway

