Related Experiment Video
Updated: Jul 25, 2025
MS2-Affinity Purification Coupled with RNA Sequencing in Gram-Positive Bacteria
Published on: February 23, 2021
The ribosome-inactivating proteins MAP30 and Momordin inhibit SARS-CoV-2
Norman R Watts1, Elif Eren1, Ira Palmer1
1Protein Expression Laboratory, NIAMS, NIH, Bethesda, Maryland, United States of America.
Abstract:
The continuing emergence of SARS-CoV-2 variants has highlighted the need to identify additional points for viral inhibition. Ribosome inactivating proteins (RIPs), such as MAP30 and Momordin which are derived from bitter melon (Momordica charantia), have been found to inhibit a broad range of viruses. MAP30 has been shown to potently inhibit HIV-1 with minimal cytotoxicity. Here we show that MAP30 and Momordin potently inhibit SARS-CoV-2 replication in A549 human lung cells (IC50 ~ 0.2 μM) with little concomitant cytotoxicity (CC50 ~ 2 μM). Both viral inhibition and cytotoxicity remain unaltered by appending a C-terminal Tat cell-penetration peptide to either protein. Mutation of tyrosine 70, a key residue in the active site of MAP30, to alanine completely abrogates both viral inhibition and cytotoxicity, indicating the involvement of its RNA N-glycosylase activity. Mutation of lysine 171 and lysine 215, residues corresponding to those in Ricin which when mutated prevented ribosome binding and inactivation, to alanine in MAP30 decreased cytotoxicity (CC50 ~ 10 μM) but also the viral inhibition (IC50 ~ 1 μM). Unlike with HIV-1, neither Dexamethasone nor Indomethacin exhibited synergy with MAP30 in the inhibition of SARS-CoV-2. From a structural comparison of the two proteins, one can explain their similar activities despite differences in both their active-sites and ribosome-binding regions. We also note points on the viral genome for potential inhibition by these proteins.
Insights
Bitter melon proteins MAP30 and Momordin effectively inhibit SARS-CoV-2 replication in lung cells. Their RNA N-glycosylase activity is crucial for this antiviral effect, with potential for new therapeutic strategies.
Area of Science:
- Biochemistry
- Virology
- Molecular Biology
Background:
- Emerging SARS-CoV-2 variants necessitate novel antiviral targets.
- Ribosome inactivating proteins (RIPs) from bitter melon, like MAP30 and Momordin, show broad antiviral activity.
- MAP30 has demonstrated potent HIV-1 inhibition with low cytotoxicity.
Purpose of the Study:
- To evaluate the efficacy of MAP30 and Momordin against SARS-CoV-2 replication.
- To investigate the mechanism of action and structure-activity relationships of these RIPs.
- To explore potential synergistic effects with other compounds.
Main Methods:
- In vitro assays using A549 human lung cells to determine IC50 and CC50 values.
- Site-directed mutagenesis of key residues in MAP30 (Y70, K171, K215).
- Assessment of viral inhibition and cytotoxicity with and without cell-penetration peptides and other drugs.
Main Results:
- MAP30 and Momordin potently inhibited SARS-CoV-2 replication (IC50 ~ 0.2 μM) with low cytotoxicity (CC50 ~ 2 μM).
- Mutation of Tyrosine 70 abolished both antiviral activity and cytotoxicity, confirming RNA N-glycosylase involvement.
- Mutations at Lysine 171 and 215 reduced cytotoxicity but also decreased viral inhibition.
- Cell-penetration peptides did not alter protein activity; no synergy was observed with Dexamethasone or Indomethacin.
Conclusions:
- MAP30 and Momordin are potent SARS-CoV-2 inhibitors, acting via their RNA N-glycosylase activity.
- Structural differences do not preclude similar antiviral efficacy between the two RIPs.
- These proteins represent promising candidates for developing new SARS-CoV-2 therapeutics.
More Related Videos
Related Concept Videos
01:23Types of RNA
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse functions and can be broadly classified as protein-coding or non-coding RNA. Non-coding RNAs play important roles in the regulation of gene expression in response to developmental and environmental changes. Non-coding RNAs in prokaryotes can be manipulated to develop more effective antibacterial drugs for human or animal use.
RNA...
02:28Leaky Scanning
01:29Translational Regulation
01:23RNA Interference
This process occurs naturally in cells, often through the activity of genomically-encoded microRNAs. Researchers can take advantage of this mechanism by introducing synthetic RNAs to deactivate specific genes for research or therapeutic purposes. For example, RNAi could be used...
02:47Ribozymes
Ribozymes can...
02:30siRNA - Small Interfering RNAs
In the cytoplasm, siRNA is processed from a double-stranded RNA, which comes from either endogenous DNA transcription or exogenous sources like a virus. This double-stranded RNA is then cleaved by the...