Sensor component of the NLRC4 inflammasome that specifically recognizes and binds flagellin from pathogenic bacteria. Association of pathogenic bacteria proteins drives in turn drive assembly and activation of the NLRC4 inflammasome, promoting caspase-1 activation, cytokine production and macrophage pyroptosis. The NLRC4 inflammasome is activated as part of the innate immune response to a range of intracellular bacteria (PubMed:21874021). The NLRC4 inflammasome senses Gram-negative bacteria such as L.pneumophila and P.aeruginosa, enteric pathogens S.typhimurium (Salmonella) and S.flexneri. May contribute to prevent motor-neuron apoptosis induced by a variety of signals (By similarity). Component of the NLRC4 inflammasome, at least composed of NLRC4, caspase-1 (CASP1) and some NAIP protein. (Microbial infection) Interacts with S.typhimurium (Salmonella) flagellin.