Structure of Spa15, a type III secretion chaperone from Shigella flexneri with broad specificity.
Type III secretion (TTS) systems are used by many Gram-negative pathogens to inject virulence proteins into the cells of their hosts. Several of these virulence effectors require TTS chaperones that maintain them in a secretion-competent state. Whereas most chaperones bind only one effector, Spa15 from the human pathogen Shigella flexneri and homologous chaperones bind several seemingly unrelated effectors, and were proposed to form a special subgroup. Its 1.8 A crystal structure confirms this specific classification, showing that Spa15 has the same fold as other TTS effector chaperones, but forms a different dimer. The presence of hydrophobic sites on the Spa15 surface suggests that the different Spa15 effectors all possess similar structural elements that can bind these sites. Furthermore, the Spa15 structure reveals larger structural differences between class I chaperones than previously anticipated, which does not support the hypothesis that chaperone-effector complexes are structurally conserved and function as three-dimensional secretion signals.
van Eerde
André
A
Laboratory of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Hamiaux
Cyril
C
Pérez
Javier
J
Parsot
Claude
C
Dijkstra
Bauke W
BW
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012763:Shigella flexneri / Q000737:chemistry*
D001426:Bacterial Proteins; D018832:Molecular Chaperones; D021122:Protein Subunits; D011994:Recombinant Proteins; C461380:Spa15 protein, Shigella flexneri