Protein and Peptide Letters - Volume 32, Issue 4, 2025

Protein phosphatases act as counterparts to protein kinases and are considered crucial for the homeostatic balance of cell signalling. In contrast to kinases, which can be categorized according to their substrate specificity, phosphatases are versatile and can detect substrates with much less distinction; hence, it is challenging to identify the physiological phosphatase-substrate pair. The Oca1 of Saccharomyces cerevisiae is a putative protein tyrosine phosphatase (PTP) and is required for cell cycle arrest in response to oxidative stress. The Oca1 mutants are sensitive to mTOR inhibitors, such as caffeine and rapamycin, and are involved in the regulation of TOR function. In an earlier research work, the enzyme exhibited no in vitro phosphatase activity and it was suggested that post-translational modifications or additional factors are necessary for it to be functional.

The modeling of Oca1 was performed to gain insight into the structural aspects. The full-length enzyme, as well as the enzyme without the N-terminal extension, was cloned, expressed, and purified to homogeneity. The structure, function, and stability of the purified enzyme were assessed using circular dichroism, fluorescence, and visible spectroscopy studies.

The Oca1 was expressed and purified from Escherichia coli. The enzyme has been found to be functional, stable, and exist in an extended monomeric form, with a molecular mass of about 27 kDa. The enzyme without the extended N-terminal random coil has also been functional and slightly more stable than the full-length Oca1.

The purified functional enzyme may be used to gain insights into the biochemical aspects and its role in bioengineering.

Diminazene aceturate (DIZE) was described as an angiotensin-converting enzyme 2 (ACE2) activator. ACE2/Angiotensin-(1-7)/Mas receptor axis presents protective actions on cardiovascular diseases and plays an important modulatory role in the neurobiology of mood and anxiety disorders.

To evaluate the effects of chronic intracerebroventricular (ICV) treatment with DIZE on blood pressure, anxiety- and depression-like behaviors in hypertensive transgenic (mRen2)27 rats (TGR).

Male TGR and Sprague-Dawley rats (10-12 weeks old) were subjected to chronic ICV infusion of DIZE (1.0 µg/h for 7 days). Blood pressure and heart rate were measured by tail plethysmography and anxiety- and depression-like behaviors were evaluated through elevated plus maze, marble burying and forced swim tests, respectively.

Treatment with DIZE induced a significant reduction in mean arterial pressure in both TGR and SD rats. A decrease in heart rate was only observed in the hypertensive animals. Additionally, treatment with DIZE attenuated the anxiety- and depression-like behaviors that were observed in TGR.

DIZE has central anti-hypertensive, anxiolytic, and anti-depressive effects.

This study compares the activity of BRCA-1 mimetics on WTp53 (wild-type p53 protein) and MTp53 (mutated-type p53 protein) proteins, examining the impact of TP53 mutations in breast cancer. p53 activators can be a new insight and synthesis of effective compounds for the treatment of cancer. The project contributes to the growing body of research on p53 activators and provides new insights into the design and synthesis of effective compounds for the treatment of cancer.

Molecular docking predicted binding affinity values for WTp53 and MTp53. The MM-GBSA of top compounds was run to get binding-free energies. The MD simulations were calculated, and six metal coordinates were synthesized. In vitro MTT-assays were performed with WTp53 (MCF-7) and R273H-MTp53 (MDA-MB-468) cell lines, comparing results with known p53 activator PRIMA-1 (p53-reactivation and induction of massive apoptosis-1).

The p53 activators established a three-featured (2RA, 1HBA) pharmacophore. The designed compounds had better Glide gscore compared to p53 activators PRIMA-1, PRIMA-1-MET (methylated PRIMA-1), and Tamoxifen with p53 protein (WTp53, R175H and R273H MTp53). The MM-GBSA results of top compounds showed binding free energies with R175H-MTp53 (-22.24 to -75.45 kcal/mol), R273H-MTp53 (-22.8 to -36.36 kcal/mol), and WTp53 (-26.45 to -50.3 kcal/mol) compared to the p53 activator. The MD simulation of TSCO5/3KMD-MT in 100 ns indicated a stable complex when compared to TSCO5/3KMD-WT. The six metal coordinates (TSCO5-Zn, TSCO6-Zn, TSCO6-Sn, TSCO13-Zn, TSCO13-Sn, TSCO9-Sn) were synthesised. Based on in vitro results, IC50 for TSCO5-Zn (WTp53: 0.089 μM, MTp53: 0.074 μM) and TSCO5-Sn (WTp53: 0.092 μM, MTp53: 0.073 μM) have shown significant cytotoxicity.

As compared to PRIMA-1, the designed compound TSCO5 metal coordinates have shown good in silico and in vitro activity on mutated p53 cell lines and are more potent than the p53 activator PRIMA-1.

Ubiquitin and ubiquitin-like systems play crucial roles across a wide range of organisms, from simple to complex. Among the three enzyme-mediated post-translational modification (PTM) steps, the ligation step is the most critical. HERC5, a member of the HECT ligase family, is one of the three enzymes involved in the ISGylation system. However, the precise start points and lengths of the HECT domains in HECT ligases are still under debate.

Some studies suggest the inclusion of an additional N-terminal alpha helix region within the HECT domain. To investigate the structural biology of the HECT domain of HERC5, we produced and purified various lengths of the HERC5 HECT domain using different fusion proteins. This approach allowed us to explore the role of the N-terminal alpha helix in the stability of the HECT domain. Our experiments successfully produced and purified HERC5 HECT domains of different lengths with various fusion proteins.

The findings demonstrated that the N-terminal alpha-helix does not enhance the stability of the HECT domain. These results challenge the notion that the N-terminal alpha-helix should be generally included in the HECT domain across all HECT ligases.

The inclusion of this region within the HECT domain may not be appropriate for generalization, as it does not contribute to stability, contrary to some previous suggestions.

Since the Coronavirus Disease (COVID-19) became a pandemic in late 2019, vaccination remains the primary approach to combating the virus. Nevertheless, the emergence of new variants poses challenges to vaccine efficacy. This study aimed to identify targets within the SARS-CoV-2 spike (S) protein to detect T-cell responses to the five variants of concern from SARS-CoV-2: Alpha, Beta, Delta, Gamma, and Omicron.

Herein, immunoinformatics tools were employed to develop a peptide-based vaccine targeting the spike protein of SARS-CoV-2 and its major variants, including Alpha, Beta, Delta, Gamma, and Omicron. The peptides were screened for antigenicity, toxicity, allergenicity, and physicochemical properties to ensure their safety and efficacy.

The potential T-cell epitopes with high immunogenicity and IFN-γ induction, are essential for a robust immune response by a comprehensive computational analysis. Population coverage analysis revealed significant coverage across diverse geographical regions, with significant efficacy in areas heavily impacted by the pandemic. Molecular docking simulations revealed strong interactions between the selected peptides and major histocompatibility complex class I (MHC-I) molecules, indicating their potential as vaccine candidates.

Our study provides a systematic approach to the rational design of a peptide-based vaccine against COVID-19, providing insights for further experimental validation and development of effective vaccines.