Identification and characterization of DegP, a serine protease associated with the luminal side of the thylakoid membrane

Hanan Itzhaki, Leah Naveh, Marika Lindahl, Mira Cook, Zach Adam*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Scopus citations

Abstract

The proteases involved in proteolytic degradation in the thylakoid lumen are largely unknown. Western analysis with an antibody against the Escherichia coli periplasmic serine protease DegP suggested that pea chloroplasts contain a homologue of this protease. This homologue was peripherally bound to the luminal side of the thylakoid membrane and could only be removed by a combination of high salt and non-ionic detergent. Its level increased almost 2-fold in pea seedlings exposed to elevated temperature for 4 h, suggesting this protease's role in the chloroplast's heat response. Isolated thylakoid membranes containing the chloroplastic homologue of DegP degraded β-casein, an in vitro substrate of the bacterial protease. This activity was partially inhibited by a serine protease inhibitor, suggesting that at least part of the casein-degrading activity in the thylakoid membrane is attributable to DegP. The existence of chloroplastic DegP was further supported by isolating a full-length Arabidopsis cDNA (designated AtDegP) encoding a protein that is 37% identical and 60% similar to the E. coli protease. The amino terminus of the deduced amino acid sequence contained a bipartite transit peptide, typical of proteins targeted to the thylakoid lumen, and the mature portion of the protein contained the highly conserved serine protease catalytic triad His- Asp-Ser. The possible physiological roles of chloroplastic DegP protease are discussed.

Original languageAmerican English
Pages (from-to)7094-7096
Number of pages3
JournalJournal of Biological Chemistry
Volume273
Issue number12
DOIs
StatePublished - 20 Mar 1998

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