DnaK interacting protein All4144 of Anabaena sp. PCC 7120: A thermo-sensor GrpE that acts as a nucleotide exchange factor and binds to DNA

This study investigates the critical role of the dimeric GrpE protein as a thermosensor within bacterial DnaK complexes, with a specific focus on All4144, a GrpE homolog found in Anabaena sp. PCC7120. In the present work, we characterized All4144, which possesses both the GrpE domain and a helix-turn-helix (HTH) domain. Our aim was to elucidate the functional significance of the HTH domain by selectively deleting the region encompassing residues 1-67 from the full-length All4144. Our findings reveal that both All4144 and its deletion mutant function as homo-dimeric nucleotide exchange factors for DnaK, enhancing the ATPase and refolding activities of DnaK. Additionally, All4144 plays a role in DNA binding. On the contrary, the deletion mutant lacking the HTH motif exhibits impaired DNA-binding ability, underscoring the importance of the HTH domain. Moreover, All4144 superior cell survival and thermal stability profiles, compared to the deletion mutant. Taken together, our study sheds light on the multifunctional nature of All4144, highlighting its pivotal role in modulating thermal tolerance through interactions with DnaK and DNA.