Redundancy and specificity of multiple trigger factor chaperones in Desulfitobacteria

Area of Science:

• Microbiology and Molecular Biology
• Protein Folding and Chaperone Function
• Bacterial Physiology and Metabolism

Background:

• Ribosome-bound trigger factor (TF) is crucial for nascent polypeptide folding and complex assembly in bacteria.
• Desulfitobacteria possess unique organohalide respiration capabilities, implying specialized protein machinery.
• The roles of TF paralogues and their specific functions in Desulfitobacteria remain largely unexplored.

Purpose of the Study:

• To investigate the presence and function of TF paralogues in Desulfitobacteria.
• To characterize the role of a truncated TF-like protein, PceT, in the maturation of reductive dehalogenases.
• To elucidate the mechanism of PceT interaction with its substrate, PceA.

Main Methods:

• Bioinformatic analysis of Desulfitobacteria genomes to identify TF paralogues.
• Heterologous expression of Desulfitobacteria TF variants in a chaperone-deficient Escherichia coli strain.
• Functional assays including suppression of growth defects and protein aggregation.
• Biochemical analysis of PceT-PceA interaction, including substrate solubilization and stabilization.
• Investigation of PceT interaction with the twin-arginine signal peptide of PceA.

Main Results:

• Multiple TF paralogues, including full-length and truncated forms, were identified in Desulfitobacteria.
• All identified TF chaperones demonstrated in vivo functionality in a heterologous system.
• The truncated TF-like protein PceT specifically chaperoned the reductive dehalogenase PceA, enhancing its solubility and stability.
• PceT was shown to interact specifically with the twin-arginine signal peptide of PceA.

Conclusions:

• Desulfitobacteria possess a diverse set of TF chaperones, including a novel truncated family (RdhT).
• PceT functions as a dedicated chaperone for reductive dehalogenases, facilitating their maturation.
• TF-like chaperones of the RdhT family are involved in the post-translational processing of proteins targeted for secretion via the twin-arginine translocation pathway.