Two types of plant NBS-LRR proteins. The two classes of NBS-LRR protein are differentiated by the N-terminal domain. TIR-NBS-LRR proteins have a Toll-interleukin-like receptor (TIR) domain, based on homology to the Drosophila Toll and mammalian Interleukin-1 (IL-1) receptors. The N-terminal region of non-TIR-NBS-LRR proteins is less defined, but often contains a coiled-coil (CC) domain. In R genes, the NBS domain plays a role in intramolecular interactions with the LRR and N-terminal domains . The N-terminal domain influences the signaling pathway that will be activated upon effector recognition , and may also be involved in pathogen recognition and interactions with targets of pathogen effectors .