Features of a twin-arginine signal peptide required for recognition by a Tat proofreading chaperone

Abstract 

The twin-arginine translocation (Tat) system is a bacterial protein targeting pathway. Tat-targeted proteins display signal peptides containing a distinctive SRRxFLK ‘twin-arginine’ motif. The Escherichia coli trimethylamine N-oxide reductase (TorA) bears a bifunctional Tat signal peptide, which directs protein export and serves as a binding site for the TorD biosynthetic chaperone. Here, the physical interaction between TorD and the TorA signal peptide was investigated. A single substitution within the TorA signal peptide (L31Q) was sufficient to impair TorD binding. Screening of a random torD mutant library identified a variant TorD protein (Q7L) that displayed increased binding affinity for the TorA signal peptide.

Structured summary

Abbreviations: Tat, twin-arginine translocation, TMAO, trimethylamine N-oxide

Keywords: Bacterial respiration, Bacterial protein targeting, Twin-arginine signal peptide, Tat proofreading chaperone, Protein–protein interaction, Site-directed mutagenesis