Fig. 4. Protein translocation into ER membranes of the Antarctic fish D. mawsoni, carp and dog. (A) Post-translational import of the truncated secretory precursor PPL86 into limiting amounts of microsomes from D. mawsoni (black), carp (grey) and dog (light grey) was assayed as described in the Materials and Methods section at the indicated temperatures. Samples were taken in duplicate and the experiment repeated twice. Translocation was defined as the percentage of signal-cleaved PL56 associated with microsomes. (B) Quantitative immunoblot of Sec61. The indicated amounts of microsomal protein were resolved on a 12.5% gel, and Sec61 was detected with polyclonal antibodies against the dog protein and [¹²⁵I]-Protein A.