1.Electronic, steric, and hydrophobic factors influencing the action of enkephalin-like peptides on opiate receptors.
Do KQ, Fauchère JL, Schwyzer R, Schiller PW, Lemieux C. Hoppe Seylers Z Physiol Chem. 1981 Jun;362(6):601-10.
The requirements of opiate receptors for electronic, steric, and hydrophobic properties of the amino acids in Pos. 4 and 5 of enkephalin-like peptides were studied. A series of [D-Ala2]-enkephalins containing carboranylalanine, adamantylalanine, t-butylglycine and p-nitrophenylalanine were synthesized and their pharmacological activities in the guinea pig ileum and their naloxone displacement in rat brain homogenates determined. An electronegative (-E) aromatic character of the amino acid in Pos. 4 strongly enhanced potency, overruling steric effects. The enhancement was not caused by exceptional enzyme resistance. Amino acid in Pos. 5 contributed to potency mainly through its effect on overall hydrophobicity. The two C-terminal amino acids seem to function as potentiator and address elements in the enkephalins.
2.Design of fluorogenic peptide substrates for human cytomegalovirus protease based on structure-activity relationship studies.
Bonneau PR1, Plouffe C, Pelletier A, Wernic D, Poupart MA. Anal Biochem. 1998 Jan 1;255(1):59-65.
Human cytomegalovirus (HCMV) protease is a slow-processing enzyme in vitro and its characterization would be facilitated if more efficiently cleaved substrates were available. Here we describe the development of improved fluorogenic peptide substrates for this protease and demonstrate that its indolent nature can be overcome by appropriate modifications within existing substrates. Prior structure-activity studies have indicated that replacement of the Val-Val-Asn sequence corresponding to the P4-P2 residues of the maturation site of the enzyme by the optimized Tbg-Tbg-Asn(NMe2) sequence conferred significant binding to inhibitors (Tbg, t-butylglycine). Incorporation of this improved sequence in a variety of substrates invariably led to improved kinetic parameters compared to homologues containing the natural sequence only. For example, the substrate o-aminobenzoyl-Tbg-Tbg-Asn (NMe2)-Ala decreases Ser-Ser-Arg-Leu-Tyr(3-NO2)Arg-OH (2) displayed a kcat/K(m) value of 15,940 M-1 s-1 i.
3.Synthesis and biological evaluation of oxytocin analogues containing L-alpha-t-butylglycine [Gly(Bu t)] in positions 8 or 9.
Fragiadaki M1, Magafa V, Slaninová J, Cordopatis P. Peptides. 2003 Sep;24(9):1425-31.
We report the solid phase synthesis and some pharmacological properties of seventeen new oxytocin (OT) analogues. Basic modification at positions 8 and/or 9 (introduction of L-alpha-t-butylglycine [Gly(Bu(t))]) was combined with D-Cys(6), D-Tyr(Et)(2), Mpa(1) or Pen(1) modifications and their various combinations. We also present properties of two previously reported re-synthesized analogues ([Gly(Bu(t))(8)]OT and [Mpa(1), Gly(Bu(t))(8)]OT). The analogues were tested for rat uterotonic activity in vitro, in the rat pressor assay and for binding affinity to human OTR.
4.Structure and function in neuropeptides.
Schwyzer R. Proc R Soc Lond B Biol Sci. 1980 Oct 29;210(1178):5-20.
This report reviews some aspects of the organization of molecular information, structure-activity relations and receptor interactions of three members of a family of neuroactive and hormonal peptides, adrenocorticotrophin (ACTH), alpha-melanotrophin (alpha-MSH) and the enkephalins, as they are presently being investigated in the author's laboratory (in collaboration with H. W. Kosterlitz, D. Schulster and P. W. Schiller). It has been established that ACTH acts on two different steroidogenically responsive receptors in rat adrenocortical cells: one that stimulates steroidogenesis without cyclic AMP synthesis and one that induces cyclic AMP production. This finding is a further example of the pleiotropic action of the opiocortin gene through different mechanisms. Another recent discovery, also related to the organization of ACTH information, reveals an unexpected interaction of ACTH(1-24) with lipid bilayer membranes: the molecule binds to the membranes in a reversible fashion and penetrates them.