Synthetic Peptides as Structural Maquettes of Angiotensin-I Converting Enzyme Catalytic Sites

The rational design of synthetic peptides is proposed as an efficient strategy for the structural investigation of crucial protein domains difficult to be produced. Only after half a century since the function of ACE was first reported, was its crystal structure solved. The main obstacle to be overcome for the determination of the high resolution structure was the crystallization of the highly hydrophobic transmembrane domain. Following our previous work, synthetic peptides and Zinc(II) metal ions are used to build structural maquettes of the two Zn-catalytic active sites of the ACE somatic isoform. Structural investigations of the synthetic peptides, representing the two different somatic isoform active sites, through circular dichroism and NMR experiments are reported

Synthesis and Biological Evaluation of New CRH Analogues

A series of 7 new human/rat Corticotropin Releasing Hormone (h/r-CRH) analogues were synthesized. The induced alterations include substitution of Phe at position 12 with D-Phe, Leu at positions 14 and 15 with Aib and Met at positions 21 and 38 with Cys(Et) and Cys(Pr). The analogues were tested regarding their binding affinity to the CRH-1 receptor and their activity which is represented by means of percentage of maximum response in comparison to the native molecule. The results indicated that the introduction of Aib, or Cys derivatives although altering the secondary structure of the molecule, did not hinder receptor recognition and binding

Peptide cell-display for selection of inhibitors against human glutathione transferase P1-1 (hGSTP1-1) allozymes

We developed a combinatorial strategy aiming at designing peptide inhibitors against the hGSTP1-1 isoenzyme involved in MDR. We developed a combinatorial strategy aiming at designing peptide inhibitors against the hGSTP1-1 isoenzyme. We employed a combinatorial peptide library featuring engineered E. coli cells harboring a plasmid able to express a fusion protein containing random 12peptides. After five selection rounds, clones were screened for hGSTP1-1 binding (dot blot hybridization) and those with the strongest signal were selected and sequenced. Sequence alignments showed a core binding sequence which, along with selected peptide fragments, were synthesized using the solid phase methodology . The synthetic peptides were studied for their inhibition potency against three human GSTP1-1 allozymes, A, B and

Combinatorial design, selection and synthesis of peptide inhibitors against human glutathione transferase p1-1

Certain glutathione S-transferase (GST) isoenzymes detoxify the cell from xenobiotics, thus becoming inhibition targets when overexpressed in various tumours leading to MDR. We developed a combinatorial strategy aiming at designing peptide inhibitors against the hGSTP1-1 isoenzyme involved in MDR. We employed a combinatorial peptide library featuring engineered E. coli cells harboring a plasmid able to express a fusion protein containing random 12 peptides which were inserted into the active loop of thioredoxin, which itself was inserted into the dispensable region of the flagellin gene. After five selection rounds, clones were screened for hGSTP1-1 binding and those with the strongest signal were selected and sequenced. Sequence alignments showed a core binding sequence which, along with selected peptide fragments, were synthesized using the solid phase methodology and Fmoc/tBu chemistry on 2-chlorotrityl chloride solid support. The four peptides were studied for their inhibition potency against hGSTP1-1 allozymes A, B and C

Synthesis of glutathione analogues and screening as substrates & inhibitors for human glutathione transferase p1‐1

A major detoxification mechanism of the cell involves the glutathione transferase (GST)‐catalyzed formation of glutathione (GSH) conjugates with various xenobiotics Based on the same mechanism, GST overexpression may lead to multidrug resistant phenotypes Therefore, several compounds with inhibitory potency against GSTs have been developed as potential tools fortackling GST-­‐attributed MDR. Several individual compounds and prodrugs have been proposed as GST‐inhibiting substances. In addition, GSH analogues have been considered as specific GST inhibitors, with particular attention been directed towards the synthesis of GSH analogues stable against γ‐glutamyltranspeptidase (γGT) and peptidases, as GST inhibitors

Electronic sculpting of ligand-GPCR subtype selectivity:the case of angiotensin II

GPCR subtypes possess distinct functional and pharmacological profiles, and thus development of subtype-selective ligands has immense therapeutic potential. This is especially the case for the angiotensin receptor subtypes AT1R and AT2R, where a functional negative control has been described and AT2R activation highlighted as an important cancer drug target. We describe a strategy to fine-tune ligand selectivity for the AT2R/AT1R subtypes through electronic control of ligand aromatic-prolyl interactions. Through this strategy an AT2R high affinity (<i>K</i>_i = 3 nM) agonist analogue that exerted 18,000-fold higher selectivity for AT2R versus AT1R was obtained. We show that this compound is a negative regulator of AT1R signaling since it is able to inhibit MCF-7 breast carcinoma cellular proliferation in the low nanomolar range

Study of a lipophilic captopril analogue binding to angiotensin I converting enzyme

International audienceHumanACE is a central component of the renin–angiotensin systemand amajor therapeutic target for cardiovascular diseases. The somatic form of the enzyme (sACE) comprises two homologous metallopeptidase domains (N and C), each bearing a zinc active site with similar but distinct substrate and inhibitor specificities. In this study, we present the biological activity of silacaptopril, a silylated analogue of captopril, and its binding affinity towards ACE. Based on the recently determined crystal structures of both the ACE domains, a series of docking calculations were carried out in order to study the structural characteristics and the binding properties of silacaptopril and its analogues with ACE

Synthesis, structural study and topological analysis of Zn/Aib and Aib-based small peptide complexes (H-Aib-OH = alpha-aminoisobutyric acid)

The systematic investigation of the coordination chemistry of alpha-aminoisobutyric acid (H-Aib-OH) and Aib-based small peptides is continued. The solid complexes [Zn-3(H-Aib-O)(6)]center dot MeCOOH center dot H2O (1 center dot MeCOOH center dot H2O), ([Zn(H-2-Aib-L-Ala-O)(2)]center dot H2O](n) (2 center dot H2O) and [Zn(H-2-Aib-Aib-Aib-O)(4)](ClO4)(2)center dot 5.8H(2)O (3 center dot 5.8H(2)O) have been isolated and characterized by single-crystal X-ray crystallography. In the structure of complex 1 center dot MeCOOH center dot H2O, three Zn-II ions and six H-Aib-O- ligands have assembled to form a trinuclear cluster. All three Zn-II centers are in a very distorted trigonal bipyramidal coordination. The trinuclear units assemble through a network of hydrogen bonds to form a 2D framework with a (3.6.3.6) topology, while the lattice acetic acid and water molecule connect the layers to create a 3D framework with a fcu topology. Complex 2 center dot H2O is a two-dimensional coordination polymer. The deprotonated dipeptide behaves as a eta(1):eta(1):eta(1):mu(2) ligand binding one Zn-II atom through its amino nitrogen and peptide oxygen, and an adjacent Zn-II atom through one of its carboxylate oxygen. In the crystal lattice, the layers are connected in the third direction through hydrogen bonds and the resulting framework conforms to a tfa net. Complex 3 center dot 5.8H(2)O consists of mononuclear [Zn(H-2-Aib-Aib-Aib-O)(4)](2+) cations, CLO4- and lattice water molecules. The tripeptide ligands are in their zwitterionic form and coordinate through one of the carboxylate oxygen atom to the metal ion, while they are participating in a network of intra- and intermolecular hydrogen bonds forming a 3D framework that adopts the bcu network. (c) 2009 Elsevier Ltd. All rights reserved