Study of the interaction of adaptor proteins with hsp100 chaperones from Arabidopsis thaliana

COLOMBO, V.; ROSANO, G. L.; BRUCH, E. M.; CECCARELLI, E. A.

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The chloroplastic proteolytic system ClpPR from Arabidopsisthaliana participates in the organelle protein quality control. It iscomposed by proteins ClpP1/3-6 and ClpR1-4, which selfassembleto delimitate a proteolytic chamber. Substratepresentation to the cavity is carried out by the Hsp100 chaperonesClpC1/2 and ClpD. They are in charge of selecting and unfoldingproteins destined for degradation and translocate them into thechamber. Three recently discovered proteins, ClpT1/2 and ClpS,are thought to be adaptors and/or regulators of the Clp system.ClpT1/2 may regulate the binding of the Hsp100 chaperones to theClpPR core and may aid in the assembly of the ClpPR complex.ClpS is proposed to modulate ClpC1/2 substrate selection andaffinity, thus expanding the range of eligible targets. However,there is little in vitro evidence to support these functions. We studiedthe interaction of recombinant ClpT1/2 and ClpS with ClpC2 andClpD by fast ultrafiltration analysis. The adaptor proteins werefound to associate with the chaperones in the presence of ATP. Theiroligomerization status was also determined. In addition, we haveinvestigated the influence of ClpT1 in the binding affinity of ClpC2to one of its substrates, the transit peptide of ferredoxin-NADP+reductase. Our results provide new insights for understanding theregulation of protein homeostasis in chloroplast.