Molecular Effects of Elongation Factor Ts and Trigger Factor on the Unfolding and Aggregation of Elongation Factor Tu Induced by the Prokaryotic Molecular Chaperone Hsp33

Abstract

Hsp33, a prokaryotic redox-regulated holding chaperone, has been recently identified to be able to exhibit an unfoldase and aggregase activity against elongation factor Tu (EF-Tu) in its reduced state. In this study, we investigated the effect of elongation factor Ts (EF-Ts) and trigger factor (TF) on Hsp33-mediated EF-Tu unfolding and aggregation using gel filtration, light scattering, circular dichroism, and isothermal titration calorimetry. We found that EF-Tu unfolding and subsequent aggregation induced by Hsp33 were evident even in its complex state with EF-Ts, which enhanced EF-Tu stability. In addition, although TF alone had no substantial effect on the stability of EF-Tu, it markedly amplified the Hsp33-mediated EF-Tu unfolding and aggregation. Collectively, the present results constitute the first example of synergistic unfoldase/aggregase activity of molecular chaperones and suggest that the stability of EF-Tu is modulated by a sophisticated network of molecular chaperones to regulate protein biosynthesis in cells under stress conditions.

Mycoplasma synoviae elongation factor thermo stable is an adhesion-associated protein that enters cells by endocytosis and stimulates DF-1 cell proliferation.

“…There are three main elongation factor types in prokaryotes: elongation factor thermo unstable (EF-Tu), EF-Ts, and elongation factor G (EF-G) [22]. EF-Ts is a guanylate exchange factor for EF-Tu that catalyzes the conversion of GDP complexed with EF-Tu to GTP and the reformation of a dimer of EF-Tu and EF-Ts (EF-T) [31,32]. EF-Tu has been identi ed as an important virulence factor in several Mycoplasma species and an immunogenic protein in M. synoviae [19,33,34].…”

Structural resemblance of the DNAJA-family protein, Tid1, to the DNAJB-family Hsp40

“…Molecular chaperones, essentially including heat shock proteins (Hsps), are recognized as a protein quality control machinery that operates to ensure cellular proteostasis (i.e., protein homeostasis) (1)(2)(3). The specific pair of Hsp70 and Hsp40, including their bacterial orthologs, DnaK and DnaJ, respectively (4), is one of the canonical chaperone systems that is ubiquitously present in all living organisms and interacts with many different substrates, via an adenine nucleotide-dependent cycle (5)(6)(7).…”