Figure 1.

P/rds is a disk rim-localized integral membrane protein with an intrinsically disordered cytoplasmic C terminus of uncertain function. A, vertebrate rod photoreceptor OS includes a stack of internalized membranous disks that are discontinuous from and enclosed by a plasma membrane. B, edges of internalized OS disks are characterized by small diameter “rims,” where the membranes are bent into hairpin-like high-curvature shapes. C, immunogold localization of P/rds to disk rims in a LR-White section of bovine retina. D, in vitro studies show that the P/rds C terminus is intrinsically disordered, but membrane mimetics can induce helical structure in its central region (18, 20, 21). The model presented here hypothesizes that a similar conformational change can be induced in situ. E, linear representations (drawn to scale) of the P/rds protein variants investigated in this study; they include WT P/rds, P/rdsΔAH (missing amino acids 310–325), and CTER, a soluble version of the cytoplasmic C terminus. Disordered regions are indicated in pink.