Design and synthesis of backbone cyclic phosphorylated peptides: The IκB model

Abstract

Phosphopeptides have been used to study phosphorylation and dephosphorylation, which are key events in protein expression. Backbone cyclization has been shown to increase the stability and selectivity of peptides. Backbone cyclic peptides with conformational diversity have produced bioactive peptides with improved pharmaceutical properties, metabolic stability, and enhanced intestinal permeability. We demonstrate a successful methodology for incorporating phospho-amino acids into backbone cyclic peptides. The nuclear factor-kappa B (NF-kappaB) is a latent mammalian protein prototype of dimeric transcription factors that exists in all cell types and plays a pivotal role in a huge number of genes, such as those responsible for chronic and acute inflammatory diseases. To inhibit NF-kappaB, backbone cyclic phosphopeptides were designed and synthesized based on the conserved sequence of the Inhibitor kappa B (IkappaB). The peptides were screened for inhibiting IkappaB ubiquitylation. The best compound showed 90% inhibition at a concentration of 3 microM, and its solution structure showed similarity to a related beta-catenin protein. This general methodology can be use for synthesizing cyclic phosphorylated, as well as backbone cyclic phosphorylated peptides for various biological targets.

Synthesis and structure–activity relationship studies of peptidomimetic PKB/Akt inhibitors: The significance of backbone interactions

“…In order to synthesize Peptoids 1a and 3a (Table 3), we used the microwave assisted reductive alkylation procedure of Park et al 35 Coupling of the Fmoc-amino acid to the hindered secondary amine was difficult, but was achieved by Fmoc-amino acid chlorides generated in situ using bis(trichloromethyl)carbonate (BTC) and 2,4,6-collidine in dibromoethane. The couplings were performed at an elevated temperature with longer reaction times [36][37][38] for Peptoids 4(a,c), 5(a,c,d) and 7(a,c,d Cleavage of Peptoids 5c and 7c gave mixtures of two products, 5(c,d) and 7(c,d), that could be easily separated by HPLC. MALDI-TOF MS analysis of the individual products revealed that the MH + species of d was 1 mass unit heavier than the MH + of c. This phenomenon has been reported earlier for N-alkylated peptide bonds, suggesting the hydrolysis of the carboxy terminal amide into the acid form.…”

Conformational Restriction of Peptides Using Dithiol Bis-Alkylation

“…This makes it very challenging to predictively design specific cross-links to stabilize a desired loop structure. Currently, identifying the proper linker chemistry, length, and positioning can only be done in an iterative process (Berthelot, Gonçalves, Laïn, Estieu-Gionnet, & Déléris, 2006; Cudic, Wade, & Otvos, 2000; Hayouka et al, 2012; Kamens, Eisert, Corlin, Baleja, & Kritzer, 2014; Qvit et al, 2009). One way to accelerate, this process is to introduce diverse conformational constraints at a late stage of synthesis.…”

Peptides that bind the HIV‐1 integrase and modulate its enzymatic activity – kinetic studies and mode of action

“…A promising approach is the use of peptides for inhibition or activation of certain viral or intracellular target proteins [21]. New emerging technologies have allowed the synthesis of cell-permeable peptides, as well as the synthesis of cyclic peptides, which are not readily susceptible to intracellular proteolysis and thus are metabolically stable [22][23][24][25][26][27][28][29][30][31][32][33]. For example, a peptide that bears the functional domain of the HIV envelope protein gp41, and competitively inhibits viral cell fusion and thus viral infection, is a Food and Drug Administration-approved anti-HIV drug [34].…”