Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 31, 1996
Publication Date: N/A
Technical Abstract: The E. coli Stress70 chaperone machine consists of three major components, products of the dnaK, dnaJ and grpE genes. DnaK is a member of the 70 kDa superfamily of heat shock proteins. DnaK is the central molecular chaperone and consists of an N-terminal ATPase domain and a C-terminal peptide recognition domain. DnaJ proteins act to increase the rate of ATP hydrolysis by DnaK in a mechanism analogous to activation of low molecular weight GTPases by the GAP proteins. GrpE proteins further accelerate the ATPase activity of DnaK by acting as nucleotide exchange factors. YdJ1p is a yeast homologue of DnaJ that is synthesized in the cytoplasm but can associate with the outer face of organellar membranes via C-terminal prenylation. We have analyzed six DnaJ homologues from Arabidopsis, AtJ1-6. AtJ1 is located within the mitochondrial matrix. AtJ2 and AtJ3 are homologues of YdJ1p, having approximately 40% sequence homology. Both of these chaperone proteins have a C-terminal -CAQQ motif, a farnesylation signal. The complete structure gene for AtJ3 was isolated and sequenced. The gene consists of six exons interrupted by five introns. AtJ6 is most similar to mammalian Hsp40. The deduced AtJ6 amino acid sequence contains the highly conserved J-domain followed by a G/F-rich sequence. It lacks, however, the C-rich region found in DnaJ homologues other than Hsp40.