Fig. 9. Inhibition of N-linked glycosylation prevents the degradation of mutant opsin. A western blot using mAb 1D4 of opsin in total protein extracts showed that inhibition of protein glycosylation with tunicamycin (0.8 µg/ml for 16 hours) led to an increase in the steady state level of mutant protein. The level of total WT opsin was not noticeably altered, whereas the level of mutant (P23H-opsin and K296E-opsin) increased significantly after treatment. The electrophoretic mobilities of different glycoforms of opsin were determined empirically using PNGase F and Endo H: mature (40 kDa) (arrowhead); and immature forms (>41 kDa); deglycosylated form (30 kDa) (^*) and dimer (60 kDa) (^**). Blot exposures have been adjusted to give equivalent band intensity between WT and mutants. The positions of the molecular weight markers are indicated on the left in kDa.