Tertiary interactions between the fifth and sixth transmembrane segments of rhodopsin

Biochemistry. 1999 May 18;38(20):6597-603. doi: 10.1021/bi9902384.


We have used cysteine scanning mutagenesis and disulfide cross-linking in a split rhodopsin construct to investigate the secondary structure and tertiary contacts of the fifth (TM5) and sixth (TM6) transmembrane segments of rhodopsin. Using a simple increase in pH to promote disulfide bond formation, three cross-links between residues on the extracellular side of TM5 (at positions 198, 200, and 204) and TM6 (at position 276) have been identified and characterized. The helical pattern of cross-linking observed indicates that the fifth transmembrane helix extends through residue 200 but does not include residue 198. Rhodopsin mutants containing these disulfides demonstrate nativelike absorption spectra and light-dependent activation of transducin, suggesting that large movements on the extracellular side of TM5 with respect to TM6 are not required for receptor activation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Absorption
  • Amino Acid Substitution / genetics
  • Animals
  • Cattle
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism
  • Cross-Linking Reagents / chemistry
  • Cysteine / genetics
  • Membrane Proteins / chemistry*
  • Membrane Proteins / metabolism
  • Mutagenesis, Site-Directed
  • Peptide Fragments / chemistry*
  • Peptide Fragments / metabolism
  • Phenylalanine / genetics
  • Protein Structure, Tertiary
  • Rhodopsin / chemistry*
  • Rhodopsin / metabolism
  • Spectrophotometry
  • Transducin / metabolism


  • Cross-Linking Reagents
  • Membrane Proteins
  • Peptide Fragments
  • Phenylalanine
  • Rhodopsin
  • Transducin
  • Cysteine