4NPH: Crystal Structure Of Ssan From Salmonella Enterica

A number of Gram-negative pathogens utilize type III secretion systems (T3SSs) to inject bacterial effector proteins into the host. An important component of T3SSs is a conserved ATPase that captures chaperone-effector complexes and energizes their dissociation to facilitate effector translocation. To date, there has been limited work characterizing the chaperone-T3SS ATPase interaction despite being a fundamental aspect of T3SS function. In this study, we present the 2.1A-resolution crystal structure of the Salmonella enterica SPI-2 encoded ATPase, SsaN. Our structure revealed a local and functionally important novel feature in helix 10 that we used to define the interaction domain relevant to chaperone binding. We modeled the interaction between the multi-cargo chaperone, SrcA, and SsaN and validated this model using mutagenesis to identify the residues on both the chaperone and ATPase that mediate the interaction. Finally, we quantified the benefit of this molecular interaction on bacterial fitness in vivo using chromosomal exchange of wild-type ssaN with mutants that retain ATPase activity, but no longer capture the chaperone. Our findings provide insight into chaperone recognition by T3SS ATPases and demonstrate the importance of the chaperone-T3SS ATPase interaction for the pathogenesis of Salmonella.
PDB ID: 4NPHDownload
MMDB ID: 121709
PDB Deposition Date: 2013/11/21
Updated in MMDB: 2014/07
Experimental Method:
x-ray diffraction
Resolution: 2.09  Å
Source Organism:
Similar Structures:
Biological Unit for 4NPH: monomeric; determined by software (PISA)
Molecular Components in 4NPH
Label Count Molecule
Protein (1 molecule)
Probable Secretion System Apparatus ATP Synthase Ssan(Gene symbol: ssaN)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB