Mutation of serine 7 does not affect NOD1 function. (A) NFκB promoter-luciferase reporter assay of NOD1 pUNO wild type (WT), S7D, S7N and E56K in HEK293 cells. 0.1 ng/well DNA was stimulated with increasing doses of the ligand, iE-DAP, or 100 ng/ml of the inactive control ligand iE-Lys (C100). Cells were incubated for 24 hours before lysis. Results show the average of three independent experiments. *** = p < 0.0005. Error bars indicate SEM. (B) Immunoblots detecting expression of NOD1 pUNO WT, S7D, S7N, E56K and vector (pUNO) in HEK293 cells. Cells were transfected with 1.5 μg DNA and incubated for 24 hours in the absence of ligand and lysed and probed with the specified antibodies. Results are representative of three independent experiments.