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Structure–function relationship studies of PTH(1–11) analogues containing sterically hindered dipeptide mimetics
Author(s) -
Fiori Nereo,
Caporale Andrea,
Schievano Elisabetta,
Mammi Stefano,
Geyer Armin,
Tremmel Peter,
Wittelsberger Angela,
Woznica Iwona,
Chorev Michael,
Peggion Evaristo
Publication year - 2007
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.872
Subject(s) - dipeptide , chemistry , steric effects , stereochemistry , parathyroid hormone , peptide , biological activity , amino acid , in vitro , biochemistry , calcium , organic chemistry
The N ‐terminal 1–34 fragment of parathyroid hormone (PTH) is fully active in vitro and in vivo and reproduces all biological responses characteristic of the native intact PTH. In order to develop safer and non‐parenteral PTH‐like bone anabolic agents, we have studied the effect of introducing conformationally constrained dipeptide mimetics into the N ‐terminal portion of PTH in an effort to generate miniaturized PTH‐mimetics. To this end, we have synthesized and conformationally and biologically characterized PTH(1–11) analogues containing 3 R ‐carboxy‐6 S ‐amino‐7,5‐bicyclic thiazolidinlactam (7,5‐bTL), a rigidified dipeptide mimetic unit. The wild type sequence of PTH(1–11) is H‐Ser‐Val‐Ser‐Glu‐Ile‐Gln‐Leu‐Met‐His‐Asn‐Leu‐NH 2 . The following pseudo‐undecapeptides were prepared: [Ala 1 , 7,5‐bTL 3, 4 , Nle 8 , Arg 11 ]hPTH(1–11)NH 2 ( I ); [Ala 1 , 7,5‐bTL 6, 7 , Nle 8 , Arg 11 ]hPTH(1–11)NH 2 ( II ); [Ala 1 , Nle 8 , 7,5‐bTL 9, 10 , Arg 11 ]hPTH(1–11)NH 2 ( III ). In aqueous solution containing 20% TFE, only analogue I exhibited the typical CD pattern of the α‐helical conformation. NMR experiments and molecular dynamics calculations located the α‐helical stretch in the sequence Ile 5 ‐His 9 . The dipeptide mimetic unit 7,5‐bTL induces a type III β‐turn, occupying the positions i − 1 and i of the turn. Analogue II exhibited an equilibrium between a type I β‐turn and an α‐helix, and analogue III did not show any ordered structure. Biological tests revealed poor activity for all analogues (EC 50 > 0.1 m M ). Apparently, the relative side‐chain orientation of Val 2 , Ile 5 and Met 8 can be critical for effective analogue‐receptor interaction. Considering helicity as an essential property to obtain active PTH agonists, one must decorate the correctly positioned dipeptide mimetic azabicycloalkane scaffold with substitutions corresponding to the displaced amino acids. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.