Structural models of intrinsically disordered and calcium-bound folded states of a protein adapted for secretion

Many Gram-negative bacteria use Type I secretion systems, T1SS, to secrete virulence factors that contain calcium-binding Repeat-in-ToXin (RTX) motifs. Here, we present structural models of an RTX protein, RD, in both its intrinsically disordered calcium-free Apo-state and its folded calcium-bound H...

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Bibliographic Details
Published in:Scientific reports 2015-09, Vol.5 (1), p.14223-14223, Article 14223
Main Authors: O’Brien, Darragh P., Hernandez, Belen, Durand, Dominique, Hourdel, Véronique, Sotomayor-Pérez, Ana-Cristina, Vachette, Patrice, Ghomi, Mahmoud, Chamot-Rooke, Julia, Ladant, Daniel, Brier, Sébastien, Chenal, Alexandre
Format: Article
Language:English
Subjects:
631/1647/296
631/45/535/1261
631/57/2269
Bacteria
Biochemistry, Molecular Biology
Calcium
Calcium (extracellular)
Calcium - metabolism
chemistry/metabolism
Cytosol
Gram-negative bacteria
Humanities and Social Sciences
Intrinsically Disordered Proteins
Intrinsically Disordered Proteins - chemistry
Intrinsically Disordered Proteins - metabolism
Life Sciences
Models, Molecular
multidisciplinary
Polymers
Protein Binding
Protein Conformation
Protein Folding
Protein Interaction Domains and Motifs
Protein structure
Protein Structure, Secondary
Proteins
Proteins - chemistry
Proteins - metabolism
Rigidity
Science
Secondary structure
Secretion
Structural models
Toxins
Virulence factors
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Summary:Many Gram-negative bacteria use Type I secretion systems, T1SS, to secrete virulence factors that contain calcium-binding Repeat-in-ToXin (RTX) motifs. Here, we present structural models of an RTX protein, RD, in both its intrinsically disordered calcium-free Apo-state and its folded calcium-bound Holo-state. Apo-RD behaves as a disordered polymer chain comprising several statistical elements that exhibit local rigidity with residual secondary structure. Holo-RD is a folded multi-domain protein with an anisometric shape. RTX motifs thus appear remarkably adapted to the structural and mechanistic constraints of the secretion process. In the low calcium environment of the bacterial cytosol, Apo-RD is an elongated disordered coil appropriately sized for transport through the narrow secretion machinery. The progressive folding of Holo-RD in the extracellular calcium-rich environment as it emerges form the T1SS may then favor its unidirectional export through the secretory channel. This process is relevant for hundreds of bacterial species producing virulent RTX proteins.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep14223