Notes: The protein with six membrane-spanning domains was translated using Rabbit Reticulocyte Lysate in the presence of Canine Microsomal Membranes. The protein was N-glycosylated and this glycosylation was sensitive to endoglycosidase H. Mutants containing one to all six transmembrane domain were constructed and immunoprecipitates tested for susceptibility to protease digestion and determination of membrane topology. The full protein could only be inserted cotranslationally since incubation of translation products with puromycin and the membranes produced no protection from the proteases. (1648)