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  • Review Article
  • Published:

Regulated proteolysis in Gram-negative bacteria — how and when?

Key Points

  • Proteolysis is a fast response to environmental changes. It is used by bacteria to control regulatory networks.

  • Proteolysis is an irreversible process and is therefore tightly controlled. The enzymes that carry out regulated proteolysis can coordinate substrate binding and degradation and are capable of targeting only a subset of proteins.

  • In Gram-negative bacteria, proteolysis regulates a large number of cellular processes such as the synthesis of lipopolysaccharides and the ability to grow at increased temperatures.

  • Proteolysis is crucial in the response to temperature shifts, starvation, stationary phase and envelope stress.

  • Proteolysis is a major factor in controlling regulatory circuits such as the SOS response and bacterial differentiation.

Abstract

Most bacteria live in a dynamic environment where temperature, availability of nutrients and the presence of various chemicals vary, which requires rapid adaptation. Many of the adaptive changes are determined by changes in the transcription of global regulatory networks, but this response is slow because most bacterial proteins are stable and their concentration remains high even after transcription slows down. To respond rapidly, an additional level of regulation has evolved: the degradation of key proteins. However, as proteolysis is an irreversible process, it is subject to tight regulation of substrate binding and degradation. Here we review the roles of the proteolytic enzymes in Gram-negative bacteria and how these enzymes can be regulated to target only a subset of proteins.

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Figure 1: Architecture and mechanism of ATP-dependent proteases.
Figure 2: Proteases and protein quality control.
Figure 3: Regulation of cellular processes by proteolysis.
Figure 4: Multifaceted functions of Met.
Figure 5: Proteolysis in the adaptation to temperature increases.

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Acknowledgements

We thank the anonymous reviewers and the editor for their helpful suggestions. Work in the authors' laboratory was supported by a DIP grant from the Deutsche Forschungsgemeinschaft (to E.Z.R. and D.B.), by a Marie Curie International Reintegration Grant (IRG) and by a German–Israeli Foundation (GIF) Young grant (to E.G.).

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Correspondence to Eliora Z. Ron.

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FURTHER INFORMATION

Protein databank

1KYI

2DHR

2FHH

3HWS

3M9B

3MT6

Glossary

N-end rule

The regulation of protein stability by the first amino acid of a protein. For example, the presence of a Lys or Arg severely decreases the half-life of the proteins through regulated proteolysis.

C1 compounds

Compounds that contain one C atom and are more reduced than CO2. Such compounds include methane, methanol and formaldehyde.

Stringent response

The physiological changes that are elicited by amino acid starvation.

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Gur, E., Biran, D. & Ron, E. Regulated proteolysis in Gram-negative bacteria — how and when?. Nat Rev Microbiol 9, 839–848 (2011). https://doi.org/10.1038/nrmicro2669

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