Fig. 4. A scanning analysis reveals that TM3 is adjacent to ER translocon components in the OP164 intermediate. Membrane associated OP164 integration intermediates with a single cysteine probe at residues 115, 124 or 132 within TM3 were treated with BMH and the resulting adducts analysed following immunoprecipitation as previously described. Schematic representations of the integration intermediates with the relative location of the cysteine probe (indicated by an asterisk) are presented above the gels and all symbols are as previously stated.