Post-translational protein import and folding.

Significant advances have been made over the past year in analyzing the membrane machineries for the post-translational export of proteins in bacteria and for the import of proteins into mitochondria. Another important development is the identification in mitochondria of homologs of the bacterial heat-shock proteins DnaJ and GrpE, which function together with Hsp70 in membrane translocation and folding of imported proteins. A number of gene products involved in peroxisomal protein uptake have been identified, which are now awaiting biochemical analysis.