(A) Immunoanalysis of supernatants and cellular extracts of COS-7 cells expressing Spn1. COS-7 cells were transiently transfected with a plasmid coding for wild-type Spn1 or for a mutant (Spn1-ΔKDEL) lacking the C-terminal KDEL motif. Supernatants and cellular extracts were collected 36 h after DNA addition, resolved by SDS/PAGE (10% gels), and analysed by Western blotting, using anti-Spn1 antibodies. (B) After immunodetection, the blotting membrane was stained with Coomassie Brilliant Blue, to check for equal loading. Lanes 1 and 2, supernatants from cells transfected with wild-type Spn1 or Spn1-ΔKDEL respectively. Lanes 3 and 4, extracts from cells transfected with wild-type Spn1 and Spn1-ΔKDEL respectively. Lanes 5 and 6, supernatants and extracts of untransfected control cells. M, molecular mass markers.