Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 285, Issue 44, Pages 34039-34047Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M110.135541
Keywords
-
Categories
Funding
- National Institutes of Health [F32AI-074245-03]
- National Center for Research Resources [AI-16892, RR-15301]
- United States Department of Defense Office of Basic Energy Sciences [DE-AC02-06CH11357]
Ask authors/readers for more resources
DegS is a periplasmic Escherichia coli protease, which functions as a trimer to catalyze the initial rate-limiting step in a proteolytic cascade that ultimately activates transcription of stress response genes in the cytoplasm. Each DegS subunit consists of a protease domain and a PDZ domain. During protein folding stress, DegS is allosterically activated by peptides exposed in misfolded outer membrane porins, which bind to the PDZ domain and stabilize the active protease. It is not known whether allostery is conferred by the PDZ domains or is an intrinsic feature of the trimeric protease domain. Here, we demonstrate that free DegS(Delta PDZ) equilibrates between active and inactive trimers with the latter species predominating. Substrate binding stabilizes active DegS(Delta PDZ) in a positively cooperative fashion. Mutations can also stabilize active DegS(Delta PDZ) and produce an enzyme that displays hyperbolic kinetics and degrades substrate with a maximal velocity within error of that for fully activated, intact DegS. Crystal structures of multiple DegS(Delta PDZ) variants, in functional and non-functional conformations, support a two-state model in which allosteric switching is mediated by changes in specific elements of tertiary structure in the context of an invariant trimeric base. Overall, our results indicate that protein substrates must bind sufficiently tightly and specifically to the functional conformation of DegS(Delta PDZ) to assist their own degradation. Thus, substrate binding alone may have regulated the activities of ancestral DegS trimers with subsequent fusion of the protease domain to a PDZ domain, resulting in ligand-mediated regulation.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available