INTERACTION OF THE TRANSIT PEPTIDE OF A CHLOROPLAST PRECURSOR PROTEIN WITH HSP100 CHAPERONES

BRUCH, E. M.; CECCARELLI, E. A.

Mar del Plata, Argentina

Congreso; Reunión anual de la Sociedad Argentina de Investigación Bioquímica; 2007

Sociedad Argentina de Investigación Bioquímica

Transit peptides (TP) are N-terminal extensions that route nuclear encoded proteins into plastids. Although Hsp100 chaperones have been implicated in precursor import into plastids, evidences of Hsp100-TP interaction are lacking. We have analyzed the interaction between the TP of pea ferredoxin NADP+ reductase (FNR) and several Hsp100 chaperones from A thaliana and E. coli. Four plasmids were constructed for the expression of FNR, FNR precursor (preFNR), GFP and an amino terminal TP fusion to GFP (TP-GFP). We also constructed two plasmid for the expression of two Hsp100 chaperones ClpC1 and ClpC2 from A. thaliana. In vivo E. coli fluorescence plates, protein accumulation in soluble fractions and protein aggregation into inclusion bodies were analyzed using several comparative assays. Ours results show that E. coli mutants defective in Hsp100 contained more aggregated TP-GFP and preFNR than the wild type strains. Co-expression of TP-GFP or preFNR and A. thaliana chaperones resulted in a reduction of aggregates. Controls expressing GFP and FNR showed no significant differences between wild type and Hsp100-defective E. coli. These results indicate that the TP directs the fusion proteins to degradation, in which Hsp100s are involved. We suggest that this effect is produced by an interaction between the FNR TP and Hsp100s from E. coli and A. thaliana