NOD2 is activated by MDP in a LRR domain dependent manner. Based on studies of NOD1 activation and structural data from the NLR-related scaffold Apaf-1, the LRR domain is believed to have a negative influence on NOD2 self-association (Inohara et al. 2000, Riedl & Salvesen 2007); binding of MDP is believed to cause conformational changes that free the NACHT domain, allowing oligomerization and subsequent association of other proteins. Coimmunoprecipitation experiments demonstrate that NOD1 can interact with itself (Inohara et al. 1999) via the NACHT domain (Inohara et al. 2000). NACHT domains are part of the AAA+ domain family. Members of this family form hexamers or heptamers. Based on these observations, NOD2 is generally believed to form hexamers or heptamers (Martinon & Tschopp, 2005). NOD2 oliogomerization has been observed in NOD2-transfected HEK293T cells (Zhao et al. 2007).