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Toward Parathyroid Hormone Minimization: Conformational Studies of Cyclic PTH(1−14) Analogues
The N-terminal fragment of PTH(1−34) is critical for PTH1 receptor activation. Various modifications of PTH(1−14) have been shown to result in a considerable increase in signaling potency [Shimizu et al. (2000) J. Biol. Chem. 275, 21836−21843]. Our structural investigations revealed an unusually sta...
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Published in: | Biochemistry (Easton) 2004-01, Vol.43 (3), p.690-699 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The N-terminal fragment of PTH(1−34) is critical for PTH1 receptor activation. Various modifications of PTH(1−14) have been shown to result in a considerable increase in signaling potency [Shimizu et al. (2000) J. Biol. Chem. 275, 21836−21843]. Our structural investigations revealed an unusually stable helical structure of the signaling domain (1−14), where residues 6 (Gln) and 10 (Gln or Asn) were located on the same face of the α-helix. To test whether a stable N-terminal α-helix is required for productive interaction with PTH1 receptor, we designed two conformationally restricted PTH(1−14) analogues, each containing a lactam bridge at positions 6 and 10. Specifically, substitutions Gln6 → Glu6 and Asn10 → Lys10 were introduced into the most potent [Ala1,3,12,Gln10,Har11,Trp14]PTH(1−14)NH2 agonist. Both the Glu6−Lys10 and Lys6−Glu10 lactam-bridged analogues were characterized to examine the importance of orientation of the lactam. According to biological studies [Shimizu et al. (2003) Biochemistry 42, 2282−2290], none of the 6/10 substituted analogues (linear or cyclic) remained as active as the parent peptide. However, relative to their corresponding linear peptides, lactam-bridged analogues either maintained potency or showed 6-fold improvement. High-resolution structures as determined by 1H NMR and NOE-restrained molecular dynamics simulations clearly illustrate the structural differences between the linear and cyclic PTH(1−14) fragments, supporting the hypothesis that an α-helix is the preferred bioactive conformation of the N-terminal fragment of PTH. In addition, our results demonstrate that the structural order of the very first residues (1−4) of the signaling domain plays a significant role in PTH action. |
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ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi035703i |