The hydrophobic core of twin-arginine signal sequences orchestrates specific binding to Tat-pathway related chaperones

• Published in: PloS one Vol. 7; no. 3; p. e34159
• Main Authors: Shanmugham, Anitha, Bakayan, Adil, Völler, Petra, Grosveld, Joost, Lill, Holger, Bollen, Yves J M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30.03.2012; Public Library of Science (PLoS)
• Subjects: Amino Acid Sequence; Analysis; Arginine; Arginine - chemistry; Bacteria; Binding; Binding Sites; Biodegradation; Bioinformatics; Biology; Carrier Proteins - metabolism; Chaperones; Coding; Cofactors; Cytoplasmic membranes; E coli; Enzymes; Escherichia coli; Escherichia coli - metabolism; Escherichia coli Proteins - metabolism; Fluorescence; Green fluorescent protein; Green Fluorescent Proteins - metabolism; Hydrophobicity; Iron-Sulfur Proteins - metabolism; Membrane Transport Proteins - metabolism; Molecular Chaperones - metabolism; Molecular Sequence Data; Mutagenesis; N-Oxide reductase; Oxidation-Reduction; Oxidoreductases - metabolism; Peptides; Plasmids - metabolism; Polypeptides; Proofreading; Proteases; Protection and preservation; Protein Binding; Protein Sorting Signals; Protein Structure, Tertiary; Protein Transport; Proteins; Sequence Homology, Amino Acid; Signal peptides; Surface Plasmon Resonance; Translocation; Trimethylamine
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0034159

Redox enzyme maturation proteins (REMPs) bind pre-proteins destined for translocation across the bacterial cytoplasmic membrane via the twin-arginine translocation system and enable the enzymatic incorporation of complex cofactors. Most REMPs recognize one specific pre-protein. The recognition site usually resides in the N-terminal signal sequence. REMP binding protects signal peptides against degradation by proteases. REMPs are also believed to prevent binding of immature pre-proteins to the translocon. The main aim of this work was to better understand the interaction between REMPs and substrate signal sequences. Two REMPs were investigated: DmsD (specific for dimethylsulfoxide reductase, DmsA) and TorD (specific for trimethylamine N-oxide reductase, TorA). Green fluorescent protein (GFP) was genetically fused behind the signal sequences of TorA and DmsA. This ensures native behavior of the respective signal sequence and excludes any effects mediated by the mature domain of the pre-protein. Surface plasmon resonance analysis revealed that these chimeric pre-proteins specifically bind to the cognate REMP. Furthermore, the region of the signal sequence that is responsible for specific binding to the corresponding REMP was identified by creating region-swapped chimeric signal sequences, containing parts of both the TorA and DmsA signal sequences. Surprisingly, specificity is not encoded in the highly variable positively charged N-terminal region of the signal sequence, but in the more similar hydrophobic C-terminal parts. Interestingly, binding of DmsD to its model substrate reduced membrane binding of the pre-protein. This property could link REMP-signal peptide binding to its reported proofreading function.