Characterization of histamine H1-receptor binding peptides in guinea pig brain using [125I]iodoazidophenpyramine, an irreversible specific photoaffinity probe

Proc Natl Acad Sci U S A. 1988 Apr;85(8):2743-7. doi: 10.1073/pnas.85.8.2743.


Aminophenpyramine--i.e., N-(5-[2-(4-aminophenyl)ethanamidopentyl])-N'-(4-methoxybenzyl)-N-m ethyl-N'- (2-pyridinyl)-1,2-ethanediamine, a derivative of mepyramine (pyrilamine), a typical antagonist of histamine at its H1 receptor--was synthesized and converted into [125I)iodoazidophenpyramine, a potential photoaffinity probe for the H1 receptor. In the dark, reversible binding of this probe to cerebellar membranes occurred with a Kd of 1.2 x 10(-11) M and a Bmax of 240 fmol/mg of protein and was inhibited by various H1-receptor antagonists with the expected potencies. These features establish the compound as one of the most potent H1-receptor antagonists known so far. Upon UV irradiation, 5% of the bound radioactivity was covalently incorporated into cerebellar membrane polypeptides as shown by standard NaDodSO4/PAGE. Two bands of 47 and 56 kDa were consistently labeled, labeling being prevented by various H1-receptor antagonists with the expected potencies and stereoselectivity. In the presence of protease inhibitors, labeling of the 56-kDa peptide increased at the expense of the 47-kDa peptide, suggesting that the latter was produced by hydrolysis of the former under the action of membrane proteases. In the absence of 2-mercaptoethanol, a band of 350-400 kDa appeared, apparently at the expense of the lighter bands, suggesting that the latter might be linked by one or more disulfide bridges to a higher molecular mass complex. We propose that at least part of the ligand binding domain of the histamine H1 receptor resides within a subunit of apparent molecular mass 56,000.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Affinity Labels*
  • Aminopyridines / metabolism*
  • Animals
  • Cell Membrane / metabolism
  • Cerebellum / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Guinea Pigs
  • In Vitro Techniques
  • Mercaptoethanol / pharmacology
  • Photochemistry
  • Protease Inhibitors / pharmacology
  • Pyrilamine / analogs & derivatives
  • Pyrilamine / metabolism*
  • Receptors, Histamine / metabolism*
  • Receptors, Histamine H1 / metabolism*


  • Affinity Labels
  • Aminopyridines
  • Protease Inhibitors
  • Receptors, Histamine
  • Receptors, Histamine H1
  • 3-iodo-4-azidophenpyramine
  • Mercaptoethanol
  • Pyrilamine