Identification of new protein substrates for the chloroplast ATP-dependent Clp protease supports its constitutive role in Arabidopsis
| Autor: | Tara M. Stanne, Adrian K. Clarke, Lars L. E. Sjögren, Shai Koussevitzky |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Chlorophyll
Chloroplasts Endopeptidase Clp Mutant Arabidopsis Biochemistry Adenosine Triphosphate Gene Expression Regulation Plant Protein biosynthesis Arabidopsis thaliana Electrophoresis Gel Two-Dimensional Photosynthesis Molecular Biology Heat-Shock Proteins chemistry.chemical_classification biology Arabidopsis Proteins food and beverages Cell Biology Plants Genetically Modified biology.organism_classification Plant Leaves Chloroplast Enzyme chemistry Chloroplast Proteins |
| Zdroj: | Biochemical Journal. 417:257-269 |
| ISSN: | 1470-8728 0264-6021 |
| DOI: | 10.1042/bj20081146 |
| Popis: | The ATP-dependent Clp protease in plant chloroplasts consists of a heterogeneous proteolytic core containing multiple ClpP and ClpR paralogues. In this study, we have examined in detail the only viable knockout mutant to date of one of these subunits in Arabidopsis thaliana, ClpR1. Loss of ClpR1 caused a slow-growth phenotype, with chlorotic leaves during early development that later partially recovered upon maturity. Analysis of the Clp proteolytic core in the clpR1 mutant (clpR1-1) revealed approx. 10% of the wild-type levels remaining, probably due to a relative increase in the closely related ClpR3 protein and its partial substitution of ClpR1 in the core complex. A proteomic approach using an in organello proteolytic assay revealed 19 new potential substrates for the chloroplast Clp protease. Many of these substrates were constitutive enzymes involved in different metabolic pathways, including photosynthetic carbon fixation, nitrogen metabolism and chlorophyll/haem biosynthesis, whereas others function in housekeeping roles such as RNA maturation, protein synthesis and maturation, and recycling processes. In contrast, degradation of the stress-related chloroplast proteins Hsp21 (heat-shock protein 21) and lipoxygenase 2 was unaffected in the clpR1-1 line and thus not facilitated by the Clp protease. Overall, we show that the chloroplast Clp protease is principally a constitutive enzyme that degrades numerous stromal proteins, a feature that almost certainly underlies its vital importance for chloroplast function and plant viability. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|