A proteolytic complex targets multiple cell wall hydrolases inPseudomonas aeruginosa

Abstract

21Carboxy-terminal processing proteases (CTPs) occur in all domains of life. In bacteria, 22 they have been associated with virulence, but their roles are poorly understood. One is 23 the CtpA protease of Pseudomonas aeruginosa, which is required for type III secretion 24 system function, and for virulence. Here we show that CtpA works with a previously 25 uncharacterized binding partner to degrade four substrates. The accumulation of at 26

Regulated, sequential processing by multiple proteases is required for proper maturation and release of Bordetella filamentous hemagglutinin

“…However, experiments with the Escherichia coli CtpA homolog Tsp showed that Tsp may preferentially bind substrates that possess a series of non‐polar residues or small, polar residues at the C‐terminus and that the nature of the final amino acid is most critical in substrate determination (Silber et al , ; Keiler et al , ; Keiler and Sauer, ). Although this characteristic is not required for targets of this family, as substrates that do not fit this scheme have been identified, the ECT does possesses an ultimate charged lysine, suggesting that the ECT may not serve as the CtpA substrate (Srivastava et al , ). Multiple observations suggest that a third, unidentified protease (P3) is responsible for removing C‐terminal residues to convert FhaB into a CtpA substrate.…”

“…Our data are consistent with direct interaction between CtpA and the prodomain. However, because it is likely that CtpA has multiple degradation targets, some of which may include homologs of identified target peptidoglycan hydrolases, it is possible that CtpA is necessary for prodomain degradation due to indirect effects, such as cleavage of another protein or changes in the peptidoglycan (Singh et al , ; Srivastava et al , ).…”

Structural basis of peptidoglycan endopeptidase regulation

“…Data from E. coli and P. aeruginosa point towards proteolytic turnover (44, 45); however, in E. coli this mechanism of regulation appears to be more dominant during stationary phase remodeling and its role in P. aeruginosa is unclear. Notably, deleting EP-specific proteases only causes minor phenotypes under laboratory growth conditions and does not seem to affect cell elongation in exponential phase unless severe osmotic conditions are applied (44, 45). Here, we present data suggesting a conformational switch mechanism of activation for LysM/M23 EPs to effectively regulate cell wall remodeling during cellular expansion.…”

“…The Gram-positive bacterium Bacillus subtilis (and likely other Gram-positive species as well) regulates EP activity via interactions with FtsEX and the PG synthesis elongation machinery (35–37) and additionally encodes a post-translational negative regulator, IseA (YoeB) (38), which presumably serves to tone down EP activity during cell wall stress conditions (38, 39). Much less is known about EP regulation in Gram-negative bacteria, where EPs appear to be kept in check as part of multiprotein complexes (40, 41), at the transcriptional level (42, 43) or via proteolytic degradation (44, 45). Proteolytic turnover appears to be the major mode of regulation of growth-promoting EPs (44, 45); however, phenotypes associated with the accumulation of EPs have surprisingly mild phenotypes under normal growth conditions, suggesting an additional, unexplored layer of regulation.…”

“…Much less is known about EP regulation in Gram-negative bacteria, where EPs appear to be kept in check as part of multiprotein complexes (40, 41), at the transcriptional level (42, 43) or via proteolytic degradation (44, 45). Proteolytic turnover appears to be the major mode of regulation of growth-promoting EPs (44, 45); however, phenotypes associated with the accumulation of EPs have surprisingly mild phenotypes under normal growth conditions, suggesting an additional, unexplored layer of regulation.…”