title: Structure-activity studies of Drosophila adipokinetic hormone (AKH) by a cellular expression system of dipteran AKH receptors.
abstract: Structure-activity studies for the adipokinetic hormone receptor of insects were for the first time performed in a cellular expression system. A series of single amino acid replacement analogues for the endogenous adipokinetic hormone of Drosophila melanogaster (pGlu-Leu-Thr-Phe-Ser-Pro-Asp-Trp-NH(2)) were screened for activity with a bioluminescence cellular assay, expressing the G-protein coupled receptor. For this series of peptide analogues, one amino acid of the N-terminal tetrapeptide was successively replaced by alanine, while those of the C-terminal tetrapeptide were successively substituted by glycine; other modifications included the blocked N- and C-termini that were replaced by an acetylated alanine and a hydroxyl group, respectively. The analogue series was tested on the AKH receptors of two dipteran species, D. melanogaster and Anopheles gambiae. The blocked termini of the AKH peptide probably play a minor role in receptor interaction and activation, but are considered functionally important elements to protect the peptide against exopeptidases. In contrast, the amino acids at positions 2, 3, 4 and 5 from the N-terminus all seem to be crucial for receptor activation. This can be explained by the potential presence of a β-strand in this part of the peptide that interacts with the receptor. The inferred β-strand is probably followed by a β-turn in which the amino acids at positions 5-8 are involved. In this β-turn, the residues at positions 6 and 8 seem to be essential, as their substitutions induce only a very low degree of receptor activation. Replacement of Asp(7), by contrast, does not influence receptor activation at all. This implies that its side chain is folded inside the β-turn so that no interaction with the receptor occurs.
authors.affiliation: Research Group of Functional Genomics and Proteomics, KU Leuven, Naamsestraat 59, B-3000 Leuven, Belgium. Jelle.Caers@bio.kuleuven.be
authors.forename: Jelle
authors.initials: J
authors.lastname: Caers
authors.forename: Lise
authors.initials: L
authors.lastname: Peeters
authors.forename: Tom
authors.initials: T
authors.lastname: Janssen
authors.forename: Wouter
authors.initials: W
authors.lastname: De Haes
authors.forename: Gerd
authors.initials: G
authors.lastname: Gäde
authors.forename: Liliane
authors.initials: L
authors.lastname: Schoofs
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D018027:Receptors, Glucagon / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: C533337:AKHR protein, Drosophila; D029721:Drosophila Proteins; D007301:Insect Hormones; D009842:Oligopeptides; D018027:Receptors, Glucagon; C044833:adipokinetic hormone; D011761:Pyrrolidonecarboxylic Acid