Figure 3.

Immunoblot analysis of wild-type opsin, I, of the M3 and M5 mutants, II, and of the M1, M1+, and M2 mutants III, transiently expressed in COS-1 cells in the absence (−) and presence (+) of tunicamycin (TM). DM (1% extracts of whole cells were used for wild-type opsin and the M2, M3, and M5 mutants. Because the M1 and M1+ mutants were not significantly extracted by 1% DM, the DM insoluble membrane pellet was used instead. Immunoblots were analyzed with the 1D4 antibody (24) which recognizes the C-terminal tag (I and II) or the B6–30N antibody (ref. 23; III) which recognizes an epitope at the N terminus which includes at least one of the two consensus glycosylation sites, the N2 and N15.