Folding and Assembly in Rhodopsin: Effect of Mutations in the Sixth Transmembrane Helix of the Third Cytoplasmic Loop
K D. Ridge, T Ngo, S S. Lee, N G. Abdulaev
Previous studies on bovine opsin folding and assembly have identified an amino-terminal fragment, EF(1-232), which folds and inserts into a membrane only after coexpression with its complementary carboxyl-terminal fragment, EF(233-348). To further characterize this interaction, EF(1-232) production was examined upon coexpression with carboxyl-terminal fragments of varying length and/or amino acid composition. These included fragments with incremental deletions of the third cytoplasmic loop [TH(241-348) and EF(249-348)], a fragment composed of the third cytoplasmic loop and sixth transmembrane helix [HF(233-280)], a fragment composed of the sixth and seventh transmembrane helices [FG(249-312)], and EF (233-348) and TH(241-348) fragments with Pro-267 or Trp-265 mutations. Although EF(1-232) production was independent of the third cytoplasmic loop and carboxyl-terminal tail, both the sixth and seventh transmembrane helices were essential. The effects of mutations in the sixth transmembrane helix on EF(1-232) expression were dependent on the length of the third cytoplasmic loop. Although Pro-267 mutations in (233-348) failed to stabilize EF(1-232) expression, their introduction into TH(241-348) was without discernable effects. However, Trp-265 substituteions in the EF(233-348) and TH(241-348) fragments conferred significant EF(1-232) production. Therefore, key residues in the sixth transmembrane helix may exert their effects on opsin folding, assembly, and/or function by influencing the conformation of the connecting loops.
Journal of Biological Chemistry
complementation, membrane protein, protein folding, receptor, signal transduction, vision
, Ngo, T.
, Lee, S.
and Abdulaev, N.
Folding and Assembly in Rhodopsin: Effect of Mutations in the Sixth Transmembrane Helix of the Third Cytoplasmic Loop, Journal of Biological Chemistry
(Accessed June 8, 2023)