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

Congreso; XLVII Reunión Anual SAIB; 2011

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molécular

The chloroplastic proteolytic system ClpPR from  Arabidopsis thaliana participates in the organelle protein quality control. It is composed by proteins ClpP1/3-6 and ClpR1-4, which self-assemble to delimitate a proteolytic chamber. Substrate presentation to the cavity is carried out by the Hsp100 chaperones ClpC1/2 and ClpD. They are in charge of selecting and unfolding proteins destined for degradation and translocate them into the chamber. 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 the ClpPR core and may aid in the assembly of the ClpPR complex. ClpS is proposed to modulate ClpC1/2 substrate selection and affinity, thus expanding the range of eligible targets. However, there is little in vitro evidence to support these functions. We studied the interaction of recombinant ClpT1/2 and ClpS with ClpC2 and ClpD by fast ultrafiltration analysis.  The adaptor proteins were found to associate with the chaperones in the presence of ATP. Their oligomerization status was also determined. In addition, we have investigated the influence of ClpT1 in the binding affinity of ClpC2 to one of its substrates, the transit peptide of ferredoxin-NADP+ reductase. Our results provide new insights for understanding the regulation of protein homeostasis in chloroplast.