Principal Investigator Tania Baker
Substrate Recognition
Work has helped formulate the conclusion that Clp/Hsp100 proteins recognize short regions of peptide sequence exposed on a folded protein. A short peptide from the carboxyl-terminal domain of MuA is required for its recognition by ClpX and is sufficient to convert a heterologous protein into a ClpX substrate. The ssrA degradation tag, an 11-residue peptide added cotransitionally to proteins as a result of ribosome stalling, is also sufficient to convert essentially any linked protein into a ClpX substrate. Analysis of proteins carrying these tags revealed that the tag peptides are unstructured, do not themselves destabilize proteins, and directly bind to ClpX. Using a proteomic screen to identify new substrates, we have identified more than 60 proteins that interact with ClpX (see below). Analysis of these proteins revealed the presence of five classes of ClpX-recognition motifs; one of these motifs is ssrA-like and one is MuA-like. These results represent the first description of general rules governing substrate recognition by an AAA+ ATPase.