Figure 2.

Protease sensitivity of the P/rds C-terminus in photoreceptor rod OS membranes. (A) Hypotonically lysed rod OS membranes were pretreated with 4M urea, 100 mM NaCarbonate, pH 11, or left untreated prior to limited digestion with Proteinase K at 37°C for the times indicated. Reactions were quenched by boiling in SDS buffer and were analyzed by Western blot analysis as developed with MAbC6, a monoclonal antibody directed against the P/rds C-terminus[12]. No significant increase in sensitivity was observed after treatment with 4M urea or 100 mM NaCarbonate. (B) Hypotonically lysed ROS membranes at 0.4 mg/ml were pretreated with 10mM DTT or were left untreated prior to limited digestion with Proteinase K at 37°C for the times indicated. Reactions were analyzed as described above. Pretreatment with DTT also had no significant effects on C-terminal Proteinase K sensitivity. Results suggest a lack of tertiary structure in the C-terminus.