Abstract
DnaK (Hsp70) is a major ATP-dependent chaperone that functions with two co-chaperones, a J-domain protein (JDP) and a nucleotide exchange factor to maintain proteostasis in most organisms. Here, we show that the environmental bacterium Shewanella oneidensis possesses a previously uncharacterized short JDP, AtcJ, dedicated to cold adaptation and composed of a functional J-domain and a C-terminal extension of 21 amino acids. We showed that atcJ is the first gene of an operon encoding also AtcA, AtcB and AtcC, three proteins of unknown functions. Interestingly, we found that the absence of AtcJ, AtcB or AtcC leads to a dramatically reduced growth at low temperature. In addition, we demonstrated that AtcJ interacts via its C-terminal extension with AtcC, and that AtcC binds to AtcB. Therefore, we identified a previously uncharacterized protein network that involves the DnaK system with a dedicated JDP to allow bacteria to survive to cold environment.
Highlights
DnaK (Hsp70) is a major ATP-dependent chaperone that functions with two co-chaperones, a J-domain protein (JDP) and a nucleotide exchange factor to maintain proteostasis in most organisms
We have recently shown that Hsp[90], another major chaperone, plays a crucial role for the growth of S. oneidensis at high temperature[16,17], Hsp[90] is expendable in Escherichia coli[18]
By exploring the genome of S. oneidensis, we found that it encodes a functional DnaK system composed of the DnaK chaperone, the nucleotide exchange factor GrpE, and several JDPs, including DnaJ
Summary
DnaK (Hsp70) is a major ATP-dependent chaperone that functions with two co-chaperones, a J-domain protein (JDP) and a nucleotide exchange factor to maintain proteostasis in most organisms. DnaK in bacteria or Hsp[70] in eukaryotes is a major ATP-dependent molecular chaperone playing a key role in the proteostasis network[3,4,5] It participates in the folding/unfolding, trafficking, disaggregation, and degradation of a multitude of client proteins, and DnaK is involved in almost all cellular functions, from DNA replication to cell division and metabolism. In the ADP-bound conformation of DnaK, the α-helical lid closes over the substrate in the β-sheet subdomain resulting in high-affinity binding of the substrate and low exchange rate[8,11]. The JDPs were named from the first extensively studied member of this family, DnaJ from E. coli, and they all possess a
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