Structural and functional analysis of the NLRP4 pyrin domain

Biochemistry. 2012 Sep 18;51(37):7330-41. doi: 10.1021/bi3007059. Epub 2012 Sep 6.


NLRP4 is a member of the nucleotide-binding and leucine-rich repeat receptor (NLR) family of cytosolic receptors and a member of an inflammation signaling cascade. Here, we present the crystal structure of the NLRP4 pyrin domain (PYD) at 2.3 Å resolution. The NLRP4 PYD is a member of the death domain (DD) superfamily and adopts a DD fold consisting of six α-helices tightly packed around a hydrophobic core, with a highly charged surface that is typical of PYDs. Importantly, however, we identified several differences between the NLRP4 PYD crystal structure and other PYD structures that are significant enough to affect NLRP4 function and its interactions with binding partners. Notably, the length of helix α3 and the α2-α3 connecting loop in the NLRP4 PYD are unique among PYDs. The apoptosis-associated speck-like protein containing a CARD (ASC) is an adaptor protein whose interactions with a number of distinct PYDs are believed to be critical for activation of the inflammatory response. Here, we use co-immunoprecipitation, yeast two-hybrid, and nuclear magnetic resonance chemical shift perturbation analysis to demonstrate that, despite being important for activation of the inflammatory response and sharing several similarities with other known ASC-interacting PYDs (i.e., ASC2), NLRP4 does not interact with the adaptor protein ASC. Thus, we propose that the factors governing homotypic PYD interactions are more complex than the currently accepted model, which states that complementary charged surfaces are the main determinants of PYD-PYD interaction specificity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Crystallography, X-Ray
  • Humans
  • Models, Molecular*
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Folding*
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Repetitive Sequences, Amino Acid
  • Repressor Proteins / chemistry*
  • Repressor Proteins / genetics
  • Structure-Activity Relationship


  • Adaptor Proteins, Signal Transducing
  • NLRP4 protein, human
  • Repressor Proteins