In position 7 L- and D-Tic-substituted oxytocin and deamino oxytocin: NMR study and conformational insights. 2010

Zinovia Spyranti, and Maria Fragiadaki, and Vassiliki Magafa, and Lenka Borovickova, and Georgios A Spyroulias, and Paul Cordopatis, and Jirina Slaninova
Department of Pharmacy, University of Patras, 26500, Patras, Greece.

Incorporation of L- or D-Tic into position 7 of oxytocin (OT) and its deamino analogue ([Mpa(1)]OT) resulted in four analogues, [L-Tic(7)]OT (1), [D-Tic(7)]OT (2), [Mpa(1),L-Tic(7)]OT (3) and [Mpa(1),D-Tic(7)]OT (4). Their biological properties were described by Fragiadaki et al. (Eur J Med Chem 42:799-806, 2007). Their NMR study (NOESY, TOCSY, (1)H-(13)C HSQC spectra) is presented here. Analogues 1, 3 and 4 showed partial agonistic activity, analogue 2 was pure antagonist, suggesting that a cis conformation between residues 6 and 7 of the molecule does not result in antagonistic activity. However, the reduction in agonistic activity of analogues 1, 3 and 4 in comparison to oxytocin is consistent with the reduction of the trans conformation form. Binding affinity for the human oxytocin receptor with IC(50) value of 130, 730, 103, and 380 nM for peptides 1, 2, 3, and 4, respectively, showed lower affinity in the case of D analogues. Deamination slightly increased the affinity. The existence of both cis and trans configurations of the Cys(6)-D-Tic(7) bond is supported by observation of two sets of cross-peaks for (1)H and (13)C nuclei for most of the residues of the peptide not only in NOESY and TOCSY but also in (1)H-(13)C HSQC spectra. The MS and HPLC indicate the presence of a single molecule/peptide, and NMR data thus suggest that this second set of peaks is due to the cis conformation.

UI MeSH Term Description Entries
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D008968 Molecular Conformation The characteristic three-dimensional shape of a molecule. Molecular Configuration,3D Molecular Structure,Configuration, Molecular,Molecular Structure, Three Dimensional,Three Dimensional Molecular Structure,3D Molecular Structures,Configurations, Molecular,Conformation, Molecular,Conformations, Molecular,Molecular Configurations,Molecular Conformations,Molecular Structure, 3D,Molecular Structures, 3D,Structure, 3D Molecular,Structures, 3D Molecular
D010121 Oxytocin A nonapeptide hormone released from the neurohypophysis (PITUITARY GLAND, POSTERIOR). It differs from VASOPRESSIN by two amino acids at residues 3 and 8. Oxytocin acts on SMOOTH MUSCLE CELLS, such as causing UTERINE CONTRACTIONS and MILK EJECTION. Ocytocin,Pitocin,Syntocinon
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D044005 Tetrahydroisoquinolines A group of ISOQUINOLINES in which the nitrogen containing ring is protonated. They derive from the non-enzymatic Pictet-Spengler condensation of CATECHOLAMINES with ALDEHYDES. Tetrahydro-Isoquinoline,1,2,3,4-Tetrahydroisoquinolines,Tetrahydro-Isoquinolines,Tetrahydro Isoquinoline,Tetrahydro Isoquinolines
D019906 Nuclear Magnetic Resonance, Biomolecular NMR spectroscopy on small- to medium-size biological macromolecules. This is often used for structural investigation of proteins and nucleic acids, and often involves more than one isotope. Biomolecular Nuclear Magnetic Resonance,Heteronuclear Nuclear Magnetic Resonance,NMR Spectroscopy, Protein,NMR, Biomolecular,NMR, Heteronuclear,NMR, Multinuclear,Nuclear Magnetic Resonance, Heteronuclear,Protein NMR Spectroscopy,Biomolecular NMR,Heteronuclear NMR,Multinuclear NMR,NMR Spectroscopies, Protein,Protein NMR Spectroscopies,Spectroscopies, Protein NMR,Spectroscopy, Protein NMR

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