Fig. 7. Double probe analysis of the OP164 and OP204 intermediates. Integration intermediates containing two cysteine probes, the first in TM1 (residue 56) and the second in TM3 (residue 115), were analysed by the BMH-dependent crosslinking of two previously characterised chain lengths (OP164 and OP204). Adducts were identified by immunoprecipitation, and for OP164 a novel crosslinking product corresponding to the opsin nascent chains simultaneously crosslinked to both Sec61ß and PAT-10 was observed (lane 5, ß+P). All other symbols are as previously defined.