Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/27/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Molecular chaperones of the 70-kDa heat shock protein (Hsp70) family function in protein folding, translocation of proteins across membranes, proteolysis, regulation of the heat shock response, and activation of signal transduction molecules. The Hsp70 chaperone machine consists of the central chaperone protein plus two cohort proteins. In E. coli these three components are products of the dnaK, dnaJ, and grpE genes. DnaJ and GrpE appear to regulate the ability of DnaK to bind and stabilize unfolded proteins before their release in a reaction requiring ATP hydrolysis. DnaJ stimulates the hydrolysis of DnaK-bound ATP which allows DnaK (in the ADP-bound state) to interact more strongly with unfolded proteins. GrpE acts as a "nucleotide exchange factor" to recycle DnaK into an ATP-bound state and facilitates release of substrate. There is also evidence that DnaJ can function independently as a chaperone. The genome of the model plant Arabidopsis thaliana contains at least 10 genes encoding DnaJ homologues. To date, we have isolated cDNA clones for seven A. thaliana DnaJ homologues, AtJ1-7. AtJ1 is the first mitochondrial DnaJ homologue found in higher organisms. AtJ2-5 are most like the yeast YdJ1 protein and are located in the cytoplasm or in association with the outer surface or organellar membranes. AtJ6 is likely a cytosolic/nuclear located protein. The AtJ7 encodes 18 kDa chloroplasts protein. The protein is smaller than any other DnaJ homologue and consists of only the characteristic J-region found in all DnaJ proteins. The primary structure and function of AtJ proteins from different compartments of the higher plant cell will be presented.