Structural diversity in twin-arginine signal peptide-binding proteins

Julien Maillard, Chris A. E. M. Spronk, Grant Buchanan, Verity Lyall, David J. Richardson, Tracy Palmer, Geerten W. Vuister, Frank Sargent, William M. Clemons (Editor)

    Research output: Contribution to journalArticlepeer-review

    66 Citations (Scopus)


    The twin-arginine transport (Tat) system is dedicated to the translocation of folded proteins across the bacterial cytoplasmic membrane. Proteins are targeted to the Tat system by signal peptides containing a twin-arginine motif. In Escherichia coli, many Tat substrates bind redox-active cofactors in the cytoplasm before transport. Coordination of cofactor insertion with protein export involves a "Tat proofreading" process in which chaperones bind twin-arginine signal peptides, thus preventing premature export. The initial Tat signal-binding proteins described belonged to the TorD family, which are required for assembly of N- and S-oxide reductases. Here, we report that E. coli NapD is a Tat signal peptide-binding chaperone involved in biosynthesis of the Tat-dependent nitrate reductase NapA. NapD binds tightly and specifically to the NapA twin-arginine signal peptide and suppresses signal peptide translocation activity such that transport via the Tat pathway is retarded. High-resolution, heteronuclear, multidimensional NMR spectroscopy reveals the 3D solution structure of NapD. The chaperone adopts a ferredoxin-type fold, which is completely distinct from the TorD family. Thus, NapD represents a new family of twin-arginine signal-peptide-binding proteins.
    Original languageEnglish
    Pages (from-to)15641-15646
    Number of pages6
    JournalProceedings of the National Academy of Sciences
    Issue number40
    Publication statusPublished - 2007


    • Metalloenzyme biosynthesis
    • Molecular chaperone
    • NMR solution structure
    • Protein-protein interactions
    • Twin-arginine transport pathway


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