title: The C-terminal domain of Escherichia coli trigger factor represents the central module of its chaperone activity.
abstract: In bacteria, ribosome-bound Trigger Factor assists the folding of newly synthesized proteins. The N-terminal domain (N) of Trigger Factor mediates ribosome binding, whereas the middle domain (P) harbors peptidyl-prolyl isomerase activity. The function of the C-terminal domain (C) has remained enigmatic due to structural instability in isolation. Here, we have characterized a stabilized version of the C domain (C(S)), designed on the basis of the recently solved atomic structure of Trigger Factor. Strikingly, only the isolated C(S) domain or domain combinations thereof (NC(S), PC(S)) revealed substantial chaperone activity in vitro and in vivo. Furthermore, to disrupt the C domain without affecting the overall Trigger Factor structure, we generated a mutant (Delta53) by deletion of the C-terminal 53 amino acid residues. This truncation caused the complete loss of the chaperone activity of Trigger Factor in vitro and severely impaired its function in vivo. Therefore, we conclude that the chaperone activity of Trigger Factor critically depends on its C-terminal domain as the central structural chaperone module. Intriguingly, a structurally similar module is found in the periplasmic chaperone SurA and in MPN555, a protein of unknown function. We speculate that this conserved module can exist solely or in combination with additional domains to fulfill diverse chaperone functions in the cell.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg Im Neuenheimer Feld 282, Universität Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Frieder
authors.initials: F
authors.lastname: Merz
authors.forename: Anja
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Anna
authors.initials: A
authors.lastname: Rutkowska
authors.forename: Beate
authors.initials: B
authors.lastname: Zachmann-Brand
authors.forename: Bernd
authors.initials: B
authors.lastname: Bukau
authors.forename: Elke
authors.initials: E
authors.lastname: Deuerling
mesh_terms: D001665:Binding Sites; D003600:Cytosol / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D006163:Ribonuclease T1 / Q000737:chemistry; D013696:Temperature
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D010455:Peptides; D006163:Ribonuclease T1; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase