Figure 10.

Cs sec61 mutants define two early stages of posttranslational translocation. The trimeric Sec61p complex consists of Sec61p and two smaller proteins, Sbh1p and Sss1p. The Sec61p complex and Sec62/Sec63p complex assemble to form the heptameric Sec complex (1), which binds precursor at a cytoplasmic docking site (2). After Kar2p recruitment and ATP hydrolysis (3), precursor is released from the docking site and inserts into the pore (4). Kar2p directly promotes the translocation (5) and release of precursors into the lumen (6). The drawing does not represent all the protein–protein interactions known to occur.