N-terminal modifications to AKH-I from Locusta migratoria: assessment of biological potencies in vivo and in vitro
| Autor: | Rebecca Luswata, Michael J. Lee, Ornella Cusinato, Colin H. Wheeler, Graham J. Goldsworthy |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Physiology
Stereochemistry Fat Body Clinical Biochemistry Peptide Grasshoppers Acetates Biology Biochemistry Cellular and Molecular Neuroscience Endocrinology In vivo Animals Potency chemistry.chemical_classification Lipid Mobilization Neuropeptides Acetylation Biological activity In vitro Amino acid chemistry Insect Hormones Glycine |
| Zdroj: | Regulatory Peptides. 69:69-76 |
| ISSN: | 0167-0115 |
| Popis: | To investigate the receptor tolerances to N-terminal variation, novel analogues to Locusta AKH-I (adipokinetic hormone) have been synthesized with modifications at the N-terminus. Analogues were made where the N-terminal pyroglutamyl residue was spaced further from the remainder of the molecule by the insertion of glycine residues between either pGlu 1 and Leu 2 (Gly 1a –AKH-I) or Leu 2 and Asn 3 (Gly 2a –AKH-I and Gly 2ab –AKH-I). Other modified hormones with N-terminal extensions were: (Ahx) n –AKH-I (Ahx, aminohexanoic acid); HPP(Ahx) n –AKH-I (HPP, hydroxyphenyl propionate) and Ac(Ahx) n –AKH-I (where n =0–3). Finally, acetylated and non-acetylated amino acids were substituted for pGlu 1 : Glu, Pro, Ala and Tyr. The effects of these modifications on biological potency were tested in the lipid mobilization assay in vivo and acetate uptake assay in vitro . The potency of AKH-I was reduced much more by insertion of glycine between pGlu 1 and Leu 2 , than between Leu 2 and Asn 3 , perhaps suggesting that a hydrophobic residue is required adjacent to the pGlu for biological activity. In addition, a residue N-terminal to Leu 2 is necessary for activity (i.e., [despGlu]–AKH-I is inactive) unless the free N-terminus is acetylated: Ac[despGlu]–AKH-I is active, but has low potency. The potencies of HPP(Ahx) 0–3 –AKH-I, Ac(Ahx) 1–3 –AKH-I and glycine-inserted analogues decreased consistently with increasing extension of the N-terminus away from the remainder of the molecule. However, potencies of the unblocked (Ahx) n –AKH-I analogues did not, and potency in either assay did not appear related to the number of aminohexanoic residues. Similarly, while hormonal activity was retained by substitution of pGlu 1 by Tyr, Pro, Ala or Glu in both assays, acetylation of the resulting analogues did not provide a consistent increase in potency, but actually decreased for AcGlu 1 –AKH-I compared with its unblocked analogue. HPP 1 –AKH-I was the most potent of the modified peptides tested, with almost the same potency in the assay in vitro as the natural peptide. |
| Databáze: | OpenAIRE |
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