Human anti-HMGCR antibodies immunoprecipitate full-length HMGCR and a piece corresponding to the C-terminus (aa 340–888). Immunoprecipitations were performed using 3 different 35S-methionine labeled HMGCR products: full-length (lanes 4–8), C-terminus (lanes 9–13) and N-terminus (lanes 14–18). Sera 10009, 9190 and 8050 are all from anti-100/200 kDa patients, while 488 and 495 are normal controls. Lanes 1–3 show the input IVTT products, which, in each case, was 0.4 times the amount used for the immunoprecipitation. Data shown are representative of those obtained in 2–8 separate experiments.