Immunoelectron microscopic localization of different protein C variants transfected in the CHO cells. Transfected CHO cells were examined by postembedding immunoelectron microscopy using 10 nm colloidal gold-conjugated second antibody. In the cells expressing PC407 (a, b) and PC408 (c, d), gold particles were mainly distributed in rough ER (a, c), and no gold particles were localized to the Golgi apparatus (b, d). In the cells expressing PC409, gold particles were distributed in both rough ER (e) and Golgi apparatus (f). The mock-transfected CHO cells showed no specific immunolabelling (g, h). Arrowheads, rough ER; G, Golgi apparatus; N, nucleus. Scale bar, 100 nm for a, c, e and g; 50 nm for b, d, f and h.