title: Escherichia coli thioredoxin-like protein YbbN contains an atypical tetratricopeptide repeat motif and is a negative regulator of GroEL.
abstract: Many proteins contain a thioredoxin (Trx)-like domain fused with one or more partner domains that diversify protein function by the modular construction of new molecules. The Escherichia coli protein YbbN is a Trx-like protein that contains a C-terminal domain with low homology to tetratricopeptide repeat motifs. YbbN has been proposed to act as a chaperone or co-chaperone that aids in heat stress response and DNA synthesis. We report the crystal structure of YbbN, which is an elongated molecule with a mobile Trx domain and four atypical tetratricopeptide repeat motifs. The Trx domain lacks a canonical CXXC active site architecture and is not a functional oxidoreductase. A variety of proteins in E. coli interact with YbbN, including multiple ribosomal protein subunits and a strong interaction with GroEL. YbbN acts as a mild inhibitor of GroESL chaperonin function and ATPase activity, suggesting that it is a negative regulator of the GroESL system. Combined with previous observations that YbbN enhances the DnaK-DnaJ-GrpE chaperone system, we propose that YbbN coordinately regulates the activities of these two prokaryotic chaperones, thereby helping to direct client protein traffic initially to DnaK. Therefore, YbbN may play a role in integrating the activities of different chaperone pathways in E. coli and related bacteria.
authors.affiliation: Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664, USA.
authors.forename: Jiusheng
authors.initials: J
authors.lastname: Lin
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wilson
mesh_terms: D020816:Amino Acid Motifs; D018834:Chaperonin 60 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D018834:Chaperonin 60; C494635:DnaJ protein, E coli; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D050862:Oxidoreductases Acting on Sulfur Group Donors; C510399:YbbN protein, E coli; C063842:dnaK protein, E coli