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| Braz. J. Med. Biol. Res. Nov (2006); 39(11):1399-408 | |
| Identification of the divergent calmodulin binding motif in yeast Ssb1-Hsp75 protein and in other HSP70 family members- | |
| Heinen RC, Diniz-Mendes L, Silva JT, Paschoalin VM | |
| Departamento de Bioquimica, Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil- | |
| Abstract: Yeast soluble proteins were fractionated by calmodulin-agarose affinity chromatography and the Ca2--calmodulin-binding proteins were analyzed by SDS-PAGE- One prominent protein of 66 kDa was excised from the gel, digested with trypsin and the masses of the resultant fragments were determined by MALDI-MS- Twenty-one of 38 monoisotopic peptide masses obtained after tryptic digestion were matched to the heat shock protein Ssb1-Hsp75, covering 37% of its sequence- Computational analysis of the primary structure of Ssb1-Hsp75 identified a unique potential amphipathic alpha-helix in its N-terminal ATPase domain with features of target regions for Ca2--calmodulin binding- This region, which shares 89% similarity to the experimentally determined calmodulin-binding domain from mouse, Hsc70, is conserved in near half of the 113 members of the HSP70 family investigated, from yeast to plant and animals- Based on the sequence of this region, phylogenetic analysis grouped the HSP70s in three distinct branches- Two of them comprise the non-calmodulin binding Hsp70s BIP-GR78, a subfamily of eukaryotic HSP70 localized in the endoplasmic reticulum, and DnaK, a subfamily of prokaryotic HSP70- A third heterogeneous group is formed by eukaryotic cytosolic HSP70s containing the new calmodulin-binding motif and other cytosolic HSP70s whose sequences do not conform to those conserved motif, indicating that not all eukaryotic cytosolic Hsp70s are target for calmodulin regulation- Furthermore, the calmodulin-binding domain found in eukaryotic HSP70s is also the target for binding of Bag-1 - an enhancer of ADP-ATP exchange activity of Hsp70s- A model in which calmodulin displaces Bag-1 and modulates Ssb1-Hsp75 chaperone activity is discussed- | |
| [PUBMED: 17146552] |   |
| Copyright © 2009, Tyers Lab, The Samuel Lunenfeld Research Institute, Mount Sinai Hospital, All Rights Reserved. |
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| BioGRID: A General Repository for Interaction Datasets. Chris Stark, Bobby-Joe Breitkreutz, Teresa Reguly, Lorrie Boucher, Ashton Breitkreutz, Mike Tyers. Nucleic Acids Res. Jan 1;34:D535-9. |