title: Ribosome-DnaK interactions in relation to protein folding.
abstract: Bacterial ribosomes or their 50S subunit can refold many unfolded proteins. The folding activity resides in domain V of 23S RNA of the 50S subunit. Here we show that ribosomes can also refold a denatured chaperone, DnaK, in vitro, and the activity may apply in the folding of nascent DnaK polypeptides in vivo. The chaperone was unusual as the native protein associated with the 50S subunit stably with a 1:1 stoichiometry in vitro. The binding site of the native protein appears to be different from the domain V of 23S RNA, the region with which denatured proteins interact. The DnaK binding influenced the protein folding activity of domain V modestly. Conversely, denatured protein binding to domain V led to dissociation of the native chaperone from the 50S subunit. DnaK thus appears to depend on ribosomes for its own folding, and upon folding, can rebind to ribosome to modulate its general protein folding activity.
authors.affiliation: Department of Biophysics, Molecular Biology and Genetics, University of Calcutta, 92 A. P. C. Road, India.
authors.forename: Jaydip
authors.initials: J
authors.lastname: Ghosh
authors.forename: Arunima
authors.initials: A
authors.lastname: Basu
authors.forename: Saumen
authors.initials: S
authors.lastname: Pal
authors.forename: Saheli
authors.initials: S
authors.lastname: Chowdhuri
authors.forename: Arpita
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Debashis
authors.initials: D
authors.lastname: Pal
authors.forename: Dhruba K
authors.initials: DK
authors.lastname: Chattoraj
authors.forename: Chanchal
authors.initials: C
authors.lastname: DasGupta
mesh_terms: D000818:Animals; D002256:Carbonic Anhydrases / Q000378:metabolism; D002417:Cattle; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C063842:dnaK protein, E coli; D002256:Carbonic Anhydrases