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J Biol Chem

Title:		The yeast Hsp110 Sse1 functionally interacts with the Hsp70 chaperones Ssa and Ssb
Author(s):		Shaner L; Wegele H; Buchner J; Morano KA;
Address:		"Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA"
Journal Title:		J Biol Chem
Year:		2005
Volume:		20051012
Issue:		50
Page Number:		41262 - 41269
DOI:		10.1074/jbc.M503614200
ISSN/ISBN:		0021-9258 (Print) 0021-9258 (Linking)
Abstract:		"There is growing evidence that members of the extended Hsp70 family of molecular chaperones, including the Hsp110 and Grp170 subgroups, collaborate in vivo to carry out essential cellular processes. However, relatively little is known regarding the interactions and cellular functions of Sse1, the yeast Hsp110 homolog. Through co-immunoprecipitation analysis, we found that Sse1 forms heterodimeric complexes with the abundant cytosolic Hsp70s Ssa and Ssb in vivo. Furthermore, these complexes can be efficiently reconstituted in vitro using purified proteins. Binding of Ssa or Ssb to Sse1 was mutually exclusive. The ATPase domain of Sse1 was found to be critical for interaction as inactivating point mutations severely reduced interaction with Ssa and Ssb. Sse1 stimulated Ssa1 ATPase activity synergistically with the co-chaperone Ydj1, and stimulation required complex formation. Ssa1 is required for post-translational translocation of the yeast mating pheromone alpha-factor into the endoplasmic reticulum. Like ssa mutants, we demonstrate that sse1delta cells accumulate prepro-alpha-factor, but not the co-translationally imported protein Kar2, indicating that interaction between Sse1 and Ssa is functionally significant in vivo. These data suggest that the Hsp110 chaperone operates in concert with Hsp70 in yeast and that this collaboration is required for cellular Hsp70 functions"
Keywords:		"Adenosine Triphosphatases/chemistry/*metabolism Alleles Cytosol/metabolism DNA Mutational Analysis DNA-Binding Proteins/metabolism Dimerization Electrophoresis, Polyacrylamide Gel Endoplasmic Reticulum/metabolism Fungal Proteins/metabolism HSP110 Heat-Sho;"
Notes:		"MedlineShaner, Lance Wegele, Harald Buchner, Johannes Morano, Kevin A eng Research Support, Non-U.S. Gov't 2005/10/14 J Biol Chem. 2005 Dec 16; 280(50):41262-9. doi: 10.1074/jbc.M503614200. Epub 2005 Oct 12"