Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are the intracellular pattern recognition receptors (PRRs) that trigger innate immunity and provide protection to the host against invading pathogens. NLRs are divided into three major subgroups: NALP (N-terminal, nucleotide-binding oligomerization domain [NACHT], leucine-rich repeat [LRR], and PYD-containing proteins), NOD (NACHT, LRR, and caspase activation and recruitment domain [CARD]-containing proteins), and NAIP (neuronal apoptosis inhibitor proteins). The NOD subgroup constituted of five receptor proteins, of which NOD1 is a cytosolic signaling host PRR comprising of the CARD at the central NACHT domain and a series of LRR domains at the C-terminal that recognize the pathogen-associated molecular patterns (PAMPs) and activates downstream signaling. Upon ligand recognition and binding, the downstream signaling adaptor molecule receptor-interacting serine/threonine kinase (RICK) is recruited which results in NF-κB phosphorylation and induction of cytokine gene expression.
 B.R. Sahoo et al. Activation of nucleotide-binding oligomerization domain 1 (NOD1) receptor signaling in Labeo rohita by iE-DAP and identification of ligand-binding key motifs in NOD1 by molecular modeling and docking. Appl. Biochem. Biotechnol. 2013, 170, 1282-1309.