title: Cyanobacterial ClpC/HSP100 protein displays intrinsic chaperone activity.
abstract: HSP100 proteins are molecular chaperones that belong to the broader family of AAA+ proteins (ATPases associated with a variety of cellular activities) known to promote protein unfolding, disassembly of protein complexes and translocation of proteins across membranes. The ClpC form of HSP100 is an essential, highly conserved, constitutively expressed protein in cyanobacteria and plant chloroplasts, and yet little is known regarding its specific activity as a molecular chaperone. To address this point, ClpC from the cyanobacterium Synechococcus elongatus (SyClpC) was purified using an Escherichia coli-based overexpression system. Recombinant SyClpC showed basal ATPase activity, similar to that of other types of HSP100 protein in non-photosynthetic organisms but different to ClpC in Bacillus subtilis. SyClpC also displayed distinct intrinsic chaperone activity in vitro, first by preventing aggregation of unfolded polypeptides and second by resolubilizing and refolding aggregated proteins into their native structures. The refolding activity of SyClpC was enhanced 3-fold in the presence of the B. subtilis ClpC adaptor protein MecA. Overall, the distinctive ClpC protein in photosynthetic organisms indeed functions as an independent molecular chaperone, and it is so far unique among HSP100 proteins in having both "holding" and disaggregase chaperone activities without the need of other chaperones or adaptor proteins.
authors.affiliation: Botanical Institute, Göteborg University, Box 461, 405 30 Göteborg, Sweden.
authors.forename: Fredrik I
authors.initials: FI
authors.lastname: Andersson
authors.forename: Robert
authors.initials: R
authors.lastname: Blakytny
authors.forename: Janine
authors.initials: J
authors.lastname: Kirstein
authors.forename: Kürsad
authors.initials: K
authors.lastname: Turgay
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.forename: Axel
authors.initials: A
authors.lastname: Mogk
authors.forename: Adrian K
authors.initials: AK
authors.lastname: Clarke
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D046940:Synechococcus / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C087481:ClpC protein, Bacteria; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010455:Peptides; C083616:mecA protein, Bacillus subtilis; D000251:Adenosine Triphosphatases