The 2 PAN ATPases from Halobacterium display N-ter heterogeneity and form labile complexes with the 20S proteasome.

Abstract

International audienceThe PAN proteins from Archaea represent homologs of the eukaryotic 26S proteasome regulatory ATPases. In vitro, the PAN complex has been previously shown to have a stimulatory effect on the peptidase activities of the 20S core. By using gradient ultracentrifugation experiments we found that, in cellular extracts, the 2 PAN proteins from Halobacterium do not form stable high molecular weight complexes. Only PAN B was found to associate transiently with the 20S proteasome, thus suggesting that the 2 PAN proteins are not functionally redundant. The PAN B-20S proteasome complexes associate in an ATP-dependent manner and are stabilized upon nucleotide binding. The 2 PAN were immunodetected in cellular extracts as N-ter truncated polypeptides. RNA mapping experiments and sequence analysis indicated that this process involved transcript heterogeneities and dual translational initiation mechanisms. Taken together, our results suggest that PAN N-ter modifications and their intra cellular dynamics of assembly/association may constitute important determinants of proteolysis regulation