Clp protease complexes from photosynthetic and non-photosynthetic plastids and mitochondria of plants, their predicted three-dimensional structures, and functional implications.
Tetradecameric Clp protease core complexes in non-photosynthetic plastids of roots, flower petals, and in chloroplasts of leaves of Arabidopsis thaliana were purified based on native mass and isoelectric point and identified by mass spectrometry. The stoichiometry between the subunits was determined. The protease complex 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). Three-dimensional homology modeling showed that the ClpP/R proteins fit well together in a tetradecameric complex and also indicated unique contributions for each protein. Lateral exit gates for proteolysis products are proposed. In addition, ClpS1,2, unique to land plants, tightly interacted with this core complex, with one copy of each per complex. The three-dimensional modeling show that they do fit well on the axial sites of the ClpPR cores. In contrast to plastids, plant mitochondria contained a single approximately 320-kDa homo-tetradecameric ClpP2 complex, without association of ClpR or ClpS proteins. It is surprising that the Clp core composition appears identical in all three plastid types, despite the remarkable differences in plastid proteome composition. This suggests that regulation of plastid proteolysis by the Clp machinery is not through differential regulation of ClpP/R/S gene expression, but rather through substrate recognition mechanisms and regulated interaction of chaperone-like molecules (ClpS1,2 and others) to the ClpP/R core.
Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA. jp269@cornell.edu
Jean-Benoît
JB
Peltier
Daniel R
DR
Ripoll
Giulia
G
Friso
Andrea
A
Rudella
Yang
Y
Cai
Jimmy
J
Ytterberg
Lisa
L
Giacomelli
Jaroslaw
J
Pillardy
Klaas J
KJ
van Wijk
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D049071:Endopeptidase Clp; D017343:Genes, Plant; D007525:Isoelectric Focusing; D046911:Macromolecular Substances; D008928:Mitochondria / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D010788:Photosynthesis; D010944:Plants / Q000201:enzymology* / Q000235:genetics; D018087:Plastids / Q000201:enzymology; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D046911:Macromolecular Substances; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases