Folding and Assembly in Rhodopsin: Effect of Mutations in the Sixth Transmembrane Helix of the Third Cytoplasmic Loop

Published

July 23, 1999

Author(s)

K D. Ridge, T Ngo, S S. Lee, N G. Abdulaev

Abstract

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.

Citation

Journal of Biological Chemistry

Volume

274

Issue

30

Pub Type

Journals

Keywords

complementation, membrane protein, protein folding, receptor, signal transduction, vision

Citation

Ridge, K. , Ngo, T. , Lee, S. and Abdulaev, N. (1999), Folding and Assembly in Rhodopsin: Effect of Mutations in the Sixth Transmembrane Helix of the Third Cytoplasmic Loop, Journal of Biological Chemistry (Accessed May 12, 2026)

Additional citation formats