The Effects of Side-Chain Configurations of a Retro–Inverso-Type Inhibitor on the Human T-Cell Leukemia Virus (HTLV)-1 Protease

Abstract

In this study, the effects of side-chain configurations of D-Ile residues of a retro–inverso (RI)-type inhibitor on the human T-cell leukemia virus type 1 (HTLV-1) protease containing a hydroxyethylamine dipeptide isostere were clarified. Prior to evaluation using the RI-type inhibitor, the effects of side-chain configurations of Ile residues of the substrate peptide on the HTLV-1 protease were examined to estimate the influence of side-chain configurations on enzyme activity. Based on the estimation of the influence of side-chain configurations on protease affinity, the RI-type inhibitors containing a D-allo-Ile residue in the corresponding substrate sequence, instead of a D-Ile residue, were synthesized via 9-fluorenylmethoxycarbonyl-based solid-phase peptide synthesis. Refolded recombinant HTLV-1 protease (1-116, L40I) was used for the simple and short evaluation of the inhibitory activities of the synthesized RI-type inhibitors. The results clearly indicated that mimicking the whole topology, comprising both the main- and side-chain structures of the parent inhibitor, is effective for the design of potent RI-modified protease inhibitors.

Different Mutation Tolerance of Lentiviral (HIV-1) and Deltaretroviral (BLV and HTLV) Protease Precursors

“…Enzymes containing stabilizing mutations, such as the HIV-1 PR5 [56][57][58][59][60] and HTLV-1 PR3 [34,35,39,61,62] are used in in vitro assays; therefore, we investigated precursors of stabilized proteases, as well. The stabilized enzymes showed considerably lower mutations tolerance, the number of non-processing mutants was higher in case of the HIV-1 PR5 containing stabilizing mutations as compared to the wild-type (41.7% and 14.3%, respectively), while the wild-type HTLV-1 PR3 was defective for self-processing in almost all cases.…”

Evaluating a Retro-Inverso Type Inhibitor of HTLV-1 Protease as a Competitive Inhibitor

“…Inhibitor The docking simulation of the RI-modified inhibitor with HTLV-1 protease, an aspartic protease, indicated that conversion of the side-chain configuration at Ile residues combined with the RI-conversion of the main-chain configuration, including the scissile site configuration, ensured the entire topology of the RI-modified inhibitor was similar to that of the original ligand. 8) The results suggested that a combined RIbased conversion of a transition state mimic inhibitor should yield the same mode of inhibition as the original inhibitor. The inhibitory mechanism of the resulting RI-modified inhibitor was further examined by constructing a Lineweaver-Burk plot.…”

“…The rate of cleavage for different amounts of substrate (H-KGPPVILPIQAP-NH 2 ) [S] by the recombinant HTLV-1 protease in the absence or presence of the RI-modified inhibitor (0, 25, 50, or 100 µM) was monitored during the initial 15-min reaction period using HPLC, as described previously. 8,9) The enzymatic reaction rate (v, µM/min) was obtained by monitoring a reduction in the peak area corresponding to the substrate, and the resulting 1/v was plotted against 1/[S]. The plots resulted in four straight lines with the same y-axis intercept reflecting competitive inhibition toward the protease (Fig.…”

“…In a previous study on transition state mimic inhibitors of human T-cell leukemia virus type 1 (HTLV-1), which is isolated from patients with adult T-cell leukemia/lymphoma, 5) we have demonstrated that simple RI-conversions, including L-to D-amino acid conversions, are not effective in protease inhibitors containing transition state mimics. 6,7) The results from these studies showed that a unique RI modification at a specific hydroxyethylamine dipeptide isostere, a key site of the protease inhibitor, is required for the inhibitory activity of the RI-modified inhibitor, which suggests that a specific RI modification is required to retain the topography of the parent inhibitor. Additionally, conversion of the Ile side-chain configuration is required to mimic the total topology of the original inhibitor as well as the RI-conversion of the backbone structure to improve the inhibitory activity 8) (Fig.…”

Antiviral Activity of Anthranilamide Peptidomimetics against Herpes Simplex Virus 1 and a Coronavirus

“…This streamlined production process contributes to their viability for mass production [ 33 ]. The approaches for transforming peptides into peptidomimetics within the realm of antiviral applications involve tactics such as altering terminal structures [ 34 ], substituting amide bonds with isosteric counterparts at particular locations [ 35 ], modifying amino acids [ 36 ], implementing an inverse-peptide strategy [ 37 ], and employing a cyclization strategy [ 38 ].…”