Fig. 1. Sys1p is a Golgi/endosome membrane protein. (A) A cleared yeast cell lysate (strain SEY6210) was divided into four aliquots that were treated for 15 min on ice with either lysis buffer (untreated), detergent, high salt or urea as indicated. After consecutive centrifugation at 10 000 and 100 000 g, the pellets (P10, P100) and the supernatants (S100) were subjected to immunoblot analysis with anti-Kar2p (ER marker), anti-Emp47p (Golgi marker) or anti-Sys1p antibodies. (B) The cleared lysate was centrifuged on sucrose gradients, and fractions (1–12, from top to bottom) were collected and subjected to immunoblot analysis with antibodies to the proteins shown to the left.