Minisymposium 7: Protein turnover

Abs # 17004: Characterization of the Clp protease complex in Arabidopsis plastids through reverse genetics and proteomics

Presenter:	Rudella, Andrea , ar253@cornell.edu
Authors	Rudella, Andrea  (A)   Peltier, Jean-Benoit  (A)   Ripoll, Daniel R (B)   Friso, Giulia  (A)   Cai, Yang  (A)   Ytterberg, Jimmy  (A)   Giacomelli, Lisa  (A)   van Wijk, Klaas J (A)
Affiliations:	(A): Cornell University - Plant Biology (B): Computational Biology Service Unit - Cornell Theory Center
Web Site:	http://cbsu.tc.cornell.edu/vanwijk/

Proteases in the plastids are needed to carry out protein processing, for turnover of miss-folded and damaged proteins, for down-regulation of protein concentrations and likely for regulation of plastid gene expression. We identified tetradecameric Clp protease core complexes in non-photosynthetic plastids of Brassica species and in chloroplasts of leaves of Arabidopsis thaliana. These protease complexes consisted of one to three copies of five different serine type protease Clp proteins (ClpP1,3-6) and four non-proteolytic ClpR proteins (ClpR1-4). In addition, ClpS1,2, unique to land plants, tightly interacted with this core complex, with one copy of each per complex. 3-D homology modeling showed that the ClpP/R proteins fit well together in a tetradecameric complex and suggests that ClpS1,2 fit well on the axial sites of the ClpPR cores. In contrast to plastids, plant mitochondria contained a single ~320 kDa homo-tetradecameric ClpP2 complex, without association of ClpR or ClpS proteins (Peltier, et al. (2004), J Biol Chem, 279: 4768-81). One of the ClpP genes is plastid-encoded and is essential in tobacco for shoot development. Isolation of A. thaliana T-DNA insertion mutants reveals that also nuclear encoded ClpP/R core genes are essential, without functional redundancy. TEM analysis reveals that thylakoid biogenesis is strongly impaired when ClpP/R genes are disrupted. These and related recent findings will be discussed.