Localization of prostaglandin endoperoxide synthase-1 to the endoplasmic reticulum and nuclear envelope is independent of its C-terminal tetrapeptide-PTEL

Arch Biochem Biophys. 1995 Mar 10;317(2):457-63. doi: 10.1006/abbi.1995.1188.


Prostaglandin endoperoxide H (PGH) synthases 1 and 2 are both membrane-associated proteins localized to the endoplasmic reticulum (ER) and nuclear envelope. The carboxyl terminal tetrapeptides of PGH synthases 1 and 2 are of the form -P/STEL. These sequences are similar to the -KDEL retention signal sequence characteristic of many proteins localized to the ER. To determine if the -PTEL sequence (residues 597-600) functions as an ER retention signal for ovine PGH synthase-1, we prepared and analyzed five mutants (L600N, L600R, L600V, E599Q, and delta 597), all having modifications that would be expected to alter the subcellular location of PGH synthase-1 if the -PTEL sequence were involved in ER targeting. Native ovine PGH synthase-1 and each of the five mutants were subcloned into the pSVT7 expression vector and were expressed transiently in cos-1 cells. The L600N, L600R, E599Q, and delta 597 mutants retained both cyclooxygenase and peroxidase activities. Moreover, when subjected to immunocytofluorescent staining, cos-1 cells expressing native and mutant enzymes showed similar patterns of fluorescence corresponding to ER and nuclear envelope localization. Finally, culture media bathing cos-1 cells transfected with native or mutant PGH synthases were tested for secreted PGH synthase-1 protein by Western blotting, but no PGH synthase-1 was detected in any of the culture media. Our results demonstrate that mutations in the C-terminal sequence-PTEL do not change the subcellular location of ovine PGH synthase-1. Thus, targeting of PGH synthase-1 to the ER can occur independent of its -PTEL sequence.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Blotting, Western
  • Cell Line
  • Chemical Phenomena
  • Chemistry, Physical
  • Cloning, Molecular
  • DNA, Complementary / chemistry
  • DNA, Complementary / genetics
  • Endoplasmic Reticulum / enzymology*
  • Fluorescent Antibody Technique
  • Gene Transfer Techniques
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Nuclear Envelope / enzymology*
  • Peptide Fragments / chemistry*
  • Prostaglandin-Endoperoxide Synthases / analysis*
  • Prostaglandin-Endoperoxide Synthases / chemistry*
  • Sequence Homology
  • Sheep
  • Structure-Activity Relationship


  • DNA, Complementary
  • Peptide Fragments
  • Prostaglandin-Endoperoxide Synthases