Structural basis for specific flagellin recognition by the NLR protein NAIP5

Xinru Yang, Fan Yang, Weiguang Wang, Guangzhong Lin, Zehan Hu, Zhifu Han, Yijun Qi, Liman Zhang, Jiawei Wang, Sen Fang Sui, Jijie Chai

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


The nucleotide-binding domain- and leucine-rich repeat (LRR)-containing proteins (NLRs) function as intracellular immune receptors to detect the presence of pathogen- or host-derived signals. The mechanisms of how NLRs sense their ligands remain elusive. Here we report the structure of a bacterial flagellin derivative in complex with the NLR proteins NAIP5 and NLRC4 determined by cryo-electron microscopy at 4.28 Å resolution. The structure revealed that the flagellin derivative forms two parallel helices interacting with multiple domains including BIR1 and LRR of NAIP5. Binding to NAIP5 results in a nearly complete burial of the flagellin derivative, thus stabilizing the active conformation of NAIP5. The extreme C-terminal side of the flagellin is anchored to a sterically constrained binding pocket of NAIP5, which likely acts as a structural determinant for discrimination of different bacterial flagellins by NAIP5, a notion further supported by biochemical data. Taken together, our results shed light on the molecular mechanisms underlying NLR ligand perception.

Original languageEnglish (US)
Pages (from-to)35-47
Number of pages13
JournalCell Research
Issue number1
StatePublished - Jan 1 2018
Externally publishedYes


  • NAIP5
  • NLRC4
  • cryo-EM
  • flagellin

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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