AzaGly-Appended Peptidomimetics Structurally Related to PTR6154 as Potential PKB/Akt Inhibitors

Computational Investigation of Conformational Properties of Short Azapeptides: Insights from DFT Study and NBO Analysis

Azapeptides have gained much attention due to their ability to enhance the stability and bioavailability of peptide drugs. Their structural preferences, essential to understanding their function and potential application in the peptide drug design, remain largely unknown. In this work, we systematically investigated the conformational preferences of three azaamino acid residues in tripeptide models, Ac-azaXaa-Pro-NHMe [Xaa = Asn (4), Asp (5), Ala (6)], using the popular DFT functionals, B3LYP and B3LYP-D3. A solvation model density (SMD) was used to mimic the solvation effect on the conformational behaviors of azapeptides in water. During the calculation, we considered the impact of the amide bond in the azapeptide models on the conformational preferences of models 4-6. We analyzed the effect of the HB between the side-chain main chain and main-chain main-chain on the conformational behaviors of azapeptides 4-6. We found that the predicted lowest energy conformation for the three models differs depending on the calculation methods. In the gas phase, B3LYP functional indicates that the conformers tttANP-1 and tttADP-1 of azapeptides 4 and 5 correspond to the type I of β-turn, the lowest energy conformation with all-trans amide bonds. Considering the dispersion correction, B3LYP-D3 functional predicts the conformers tctANP-2 and tctADP-3 of azapeptide 4 and 5, which contain the cis amide bond preceding the Pro residue, as the lowest energy conformation in the gas phase. The results imply that azaAsx and Pro residues may involve cis-trans isomerization in the gas phase. In water, the predicted lowest energy conformer of azapeptides 4 and 5 differs from the gas phase results and depends on the calculational method. For azapeptide 6, regardless of calculation methods and phases, tttAAP-1 (β-I turn) is predicted as the lowest energy conformer. The results imply that the effect of the side chain that can form HBs on the conformational preferences of azapeptides 4 and 5 may not be negligible. We compared the theoretical results of azaXaa-Pro models with those of Pro-azaXaa models, showing that incorporating azaamino acid residue in peptides at different positions can significantly impact the folding patterns and stability of azapeptides.

Facile synthesis of rapamycin-peptide conjugates as mTOR and Akt inhibitors

A simple and straightforward process for the synthesis of rapamycin peptide conjugates in a regio and chemoselective manner was developed. The methodology comprises the tagging of chemoselective functionalities to rapamycin and peptides which enables the conjugation of free peptides, without protecting the functionality of the side chain amino acids, in high yield and purity. From this methodology, we successfully conjugate free peptides containing up to 15 amino acids. Rapamycin is also conjugated to the peptides known for inhibiting the kinase activity of Akt protein. These conjugates act as dual target inhibitors and inhibit the kinase activity of both mTOR and Akt.

Synthesis and biological activity of Ub2 derived peptides as potential host-directed antitubercular therapy

The correlation of mycobactericidal property of macrophages with its potential to deliver bacteria to hydrolytic lysosomes, augmented with ubiquitin-derived peptides (Ub2), activates the process of autophagy. This leads to the formation of phagolysosomes supported by factor involving increased cationic charges which regulate the acidic pH causing elimination of Mycobacterium. To better understand this interaction of cationic-rich ubiquitin-derived peptides with mycobacteria and to identify putative mycobacterial intrinsic resistance mechanisms for phagolysosome formation, we have synthesized a new series of Ub2 peptides, wherein the Gly residues are replaced with azaGly with the aim to improve metabolic stability. In addition to that a new methodology is reported for the synthesis of heteroaryl tethered peptides using azaGly as a linker. We have demonstrated that positive puncta (directly proportional to the acidification of lysosome) in cytosol was significantly increased after 6 hours on the treatment of macrophage with Ub2 peptide derivatives (1, 6, 10, and 11) causing the higher intensity of lysosome observed through LysoTracker Red Dye. The circular dichroism spectral studies are carried out in water and water:TFE mixture and demonstrated that the Ub2 peptides have helix-forming tendency in the presence of TFE. The recognizable intracellular killing of Mycobacterium tuberculosis by Ub2 peptides provides a new approach for host-directed therapy.