title: Thermostability of two cyanobacterial GrpE thermosensors.
abstract: GrpE proteins act as co-chaperones for DnaK heat-shock proteins. The dimeric protein unfolds under heat stress conditions, which results in impaired interaction with a DnaK protein. Since interaction of GrpE with DnaK is crucial for the DnaK chaperone activity, GrpE proteins act as a thermosensor in bacteria. Here we have analyzed the thermostability and function of two GrpE homologs of the mesophilic cyanobacterium Synechocystis sp. PCC 6803 and of the thermophilic cyanobacterium Thermosynechococcus elongatus BP1. While in Synechocystis an N-terminal helix pair of the GrpE dimer appears to be the thermosensing domain and mainly mediates GrpE dimerization, the C-terminal four-helix bundle is involved in additional stabilization of the dimeric structure. The four-helix bundle domain has a key role in the thermophilic cyanobacterium, since dimerization of the Thermosynechococcus protein appears to be mediated by the four-helix bundle domain, and melting of this domain is linked to monomerization of the GrpE protein. Thus, in two related cyanobacteria the GrpE thermosensing function might be mediated by different protein domains.
authors.affiliation: Institut für Pharmazie und Biochemie, Johannes Gutenberg-Universität, Johann-Joachim-Becher-Weg 30, D-55128 Mainz, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Barthel
authors.forename: Eva
authors.initials: E
authors.lastname: Rupprecht
authors.forename: Dirk
authors.initials: D
authors.lastname: Schneider
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002942:Circular Dichroism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D000458:Cyanobacteria / Q000187:drug effects / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D046939:Synechocystis / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; C068113:GrpE protein, Bacteria; D006360:Heat-Shock Proteins