Chloroplast proteases: Possible regulators of gene expression?

Zach Adam*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


A wide range of proteolytic processes in the chloroplast are well recognized. These include processing of precursor proteins, removal of oxidatively damaged proteins, degradation of proteins missing their prosthetic groups or their partner subunit in a protein complex, and adjustment of the quantity of certain chloroplast proteins in response to changing environmental conditions. To date, several chloroplast proteases have been identified and cloned. The chloroplast processing enzyme is responsible for removing the transit peptides of newly imported proteins. The thylakoid processing peptidase removes the thylakoid-transfer domain from proteins translocated into the thylakoid lumen. Within the lumen, Tsp removes the carboxy-terminal tail of the precursor of the PSII D1 protein. In contrast to these processing peptidases which perform a single endo-proteolytic cut, processive proteases that can completely degrade substrate proteins also exist in chloroplasts. The serine ATP-dependent Clp protease, composed of the proteolytic subunit ClpP and the regulatory subunit ClpC, is located in the stroma, and is involved in the degradation of abnormal soluble and membrane-bound proteins. The ATP-dependent metalloprotease FtsH is bound to the thylakoid membrane, facing the stroma. It degrades unassembled proteins and is involved in the degradation of the D1 protein of PSII following photoinhibition. DegP is a serine protease bound to the lumenal side of the thylakoid membrane that might be involved in the chloroplast response to heat. All these peptidases and proteases are homologues of known bacterial enzymes. Since ATP-dependent bacterial proteases and their mitochondrial homologues are also involved in the regulation of gene expression, via their determining the levels of key regulatory proteins, chloroplast proteases are expected to play a similar role. (C) 2000 Societe francaise de biochimie et biologie moleculaire / Editions scientifiques et medicales Elsevier SAS.

Original languageAmerican English
Pages (from-to)647-654
Number of pages8
Issue number6-7
StatePublished - 2000

Bibliographical note

Funding Information:
Work in the author’s laboratory was supported by grants from the Israel Science Foundation, the US-Israel Binational Science Foundation (BSF), the US-Israel Binational Agricultural Research and Development Fund (BARD), and a joint grant from the European Union and the Israeli Ministry of Science.


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