Reddy Vemuri B, Iuga Aurel O, Kounga Kounga, Lerner Ethan A
Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
J Biol Chem. 2006 Jun 16;281(24):16197-201. doi: 10.1074/jbc.M509429200. Epub 2006 Mar 28.
Maxadilan, a 61-amino-acid vasodilatory peptide, was initially isolated from the salivary glands of the sand fly Lutzomyia longipalpis. Although its primary sequence has no homology to that of pituitary adenylate cyclase-activating peptide, maxadilan is an agonist for the PAC1 receptor. A total of 58 substitution and deletion mutants was engineered in an effort to determine which residues were important for receptor activation. The mutants were characterized functionally using an assay based on pigment granule translocation in PAC1-expressing Xenopus laevis melanophores. Substitution of charged residues and proline 43 could alter (but not eliminate) the agonist activity of the mutants. In contrast, we found that several multiple substitution mutants of the predicted beta-strand threonine residues became antagonists at the PAC1 receptor. The results suggest that these threonine residues are cooperatively involved in PAC1 activation.
