Protein folding has often been assumed to be a spontaneous process, a classic example of biological "self-assembly". However, it has recently become apparent that protein folding and assembly of multimeric protein complexes can be catalyzed by other proteins. the highly conserved heat shock proteins (HSPs) comprise one class of these so-called "chaperonins". The long term goal of the proposed research is to determine the mechanism of action of the recently discovered DnaJ family of eukaryotic heat shock protein homologues. In bacteria, DnaJ interacts with and modulates the activities of DnaK, the HSP70 cognate. The proposed experiments are designed with this paradigm in mind. A combination of yeast genetics, molecular biological, and biochemical approaches will be employed. The specific aims are: 1) to determine the role of Scjs in protein translocation into organelles; 2) to define the interaction between Scjs and HSP70s; 3) to test the hypothesis that each eukaryotic HSP70 will have one or more like DnaJ-like partners; and 4) to dissect the proposed domain organization of Scjs.