To further characterize the human thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptor, preparative isoelectric focusing (IEF) was performed on solubilized platelet membranes. TXA2/PGH2 receptors, assayed by specific binding of the TXA2/PGH2 antagonist [125I]PTA-OH, were electrofocused at pH 5.6. Scatchard analysis of IEF fraction pH 5.6 revealed a 180-fold concentration of TXA2/PGH2 receptors (Bmax=3650±228 pM/mg focused, 19±4 pM/mg unfocused) with no change in binding affinity (Kd=47±7 nM focused, 36±14 nM unfocused). SDS-polyacrylamide gel electrophoresis of photoaffinity-labelled electrofocused receptors revealed concentration of specifically labelled proteins having molecular masses of 49,000 and 27,000 Daltons. These results suggest that the human platelet TXA2/PGH2 receptor has a pI of 5.6, molecular mass of 49,000 Daltons, and may exist as a dimer. Preparative IEF should prove useful in the eventual purification of this receptor.

Original languageEnglish
Pages (from-to)183-188
Number of pages6
JournalBiochemical and Biophysical Research Communications
Issue number1
StatePublished - Aug 30 1989


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