4NKH: Crystal Structure Of Ssph1 Lrr Domain

IpaH proteins are bacterium-specific E3 enzymes that function as type three secretion system (T3SS) effectors in Salmonella, Shigella, and other Gram-negative bacteria. IpaH enzymes recruit host substrates for ubiquitination via a leucine-rich repeat (LRR) domain, which can inhibit the catalytic domain in the absence of substrate. The basis for substrate recognition and the alleviation of autoinhibition upon substrate binding is unknown. Here, we report the X-ray structure of Salmonella SspH1 in complex with human PKN1. The LRR domain of SspH1 interacts specifically with the HR1b coiled-coil subdomain of PKN1 in a manner that sterically displaces the catalytic domain from the LRR domain, thereby activating catalytic function. SspH1 catalyzes the ubiquitination and proteasome-dependent degradation of PKN1 in cells, which attenuates androgen receptor responsiveness but not NF-kappaB activity. These regulatory features are conserved in other IpaH-substrate interactions. Our results explain the mechanism whereby substrate recognition and enzyme autoregulation are coupled in this class of bacterial ubiquitin ligases.
PDB ID: 4NKHDownload
MMDB ID: 115953
PDB Deposition Date: 2013/11/12
Updated in MMDB: 2013/12
Experimental Method:
x-ray diffraction
Resolution: 2.75  Å
Source Organism:
Similar Structures:
Biological Unit for 4NKH: monomeric; determined by author
Molecular Components in 4NKH
Label Count Molecule
Protein (1 molecule)
E3 Ubiquitin-protein Ligase Ssph1
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB