Comparison of NRTIs and NtRTIs mechanism uses and examples
As we all know most viruses have RNA as genetic material. Through the process of transcription, DNA makes RNA. Do you know how DNA is made from RNA? Or what is the function of reverse transcriptase enzymes? In this article, we are going to study reverse transcriptase enzymes and reverse transcriptase inhibitors, and the types of reverse transcriptase inhibitors. We will also learn about the differences and similarities between nucleoside and nucleotide reverse transcriptase.
Reverse Transcriptase
Reverse transcription is a process of converting RNA into complementary DNA. This process mostly occurs in viruses that have RNA as genetic material.
Reverse transcriptase is an enzyme used for this process. There are two types of reverse transcriptase- nucleoside and nucleotide reverse transcriptase.
Reverse Transcriptase Inhibitors
Reverse transcriptase inhibitors are drugs that inhibit the activity of reverse transcriptase enzymes and these are used to treat HIV infection.
There are mainly four forms of reverse transcriptase inhibitors.
Nucleoside reverse transcriptase inhibitors
Nucleotide reverse transcriptase inhibitors
Non-nucleoside reverse transcriptase inhibitors
Nucleoside reverse transcriptase translocation inhibitors
Nucleoside Reverse Transcriptase
Nucleoside reverse transcriptase inhibitor inhibits the activity of nucleoside reverse transcriptase enzymes. This inhibitor works by competitive inhibition and inhibits nucleoside reverse transcriptase's activity or functions. These drugs comprise the first class of antiretroviral drugs. A few examples of nucleoside reverse transcriptase inhibitors are zidovudine, stavudine, didanosine, etc.
Nucleotide Reverse Transcriptase Inhibitors
Nucleotide reverse transcriptase also works as a competitive inhibitor as nucleoside reverse transcriptase inhibitors. These are the second type of antiretroviral drugs. This drug also blocks the reverse transcriptase enzyme. Examples of nucleotide reverse transcriptase inhibitor tenofovir.
Difference Between Nucleoside and Nucleotide Reverse Transcriptase Inhibitors
Similarities Between Nucleoside and Nucleotide Reverse Transcriptase Inhibitors
Both of these drugs are used to treat antiretroviral infections.
They work by competitive inhibitions
Both these drugs work as chain terminators.
Both these types of drugs lack hydroxyl groups.
The mechanism of action of both of these drugs is the same.
These drugs may have side effects because they also act on host cells.
Side effects of these drugs are vomiting, diarrhoea, stomach problems, and headaches.
Important Questions
1. How do nucleotide and nucleoside reverse transcriptase inhibitors work?
Ans: These drugs work by blocking the reverse transcriptase inhibitors. HIV viruses use reverse transcriptase enzymes to make cDNA from RNA. Thus to treat aids disease we need to inhibit the reverse transcriptase enzyme
2. Which enzyme is used in reverse transcription?
Ans: Reverse transcriptase is the enzyme used in the process of reverse transcription.
Conclusion
Reverse transcriptase is an enzyme that converts RNA into cDNA. Reverse transcriptase inhibitors are the drugs used to inhibit the function of reverse transcriptase and hence stop the process of reverse transcription. There are four forms of reverse transcriptase inhibitors. These include nucleoside reverse transcriptase inhibitors, nucleotide reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, and nucleoside reverse transcriptase translocation inhibitors. We have also discussed the differences between nucleoside and nucleotide reverse transcriptase Inhibitors and the similarities between them.
Practice Questions
1. What is the mechanism of action of nucleoside reverse transcriptase inhibitors?
2. What are the examples of nucleoside reverse transcriptase inhibitors?
3. Why is cDNA used instead of DNA?
4. Who discovered the reverse transcription?
5. How do reverse transcripts work?
FAQs on Difference Between Nucleoside and Nucleotide Reverse Transcriptase Inhibitors
1. What is the difference between nucleoside and nucleotide reverse transcriptase inhibitors?
The main difference between nucleoside reverse transcriptase inhibitors (NRTIs) and nucleotide reverse transcriptase inhibitors (NtRTIs) is that NRTIs are nucleoside analogs without a phosphate group, while NtRTIs are nucleotide analogs that already contain one phosphate group.
- NRTIs require three phosphorylation steps inside the cell to become active.
- NtRTIs require only two phosphorylation steps because they already have one phosphate group.
- Both inhibit the viral enzyme reverse transcriptase in HIV and cause premature DNA chain termination.
2. What are nucleoside reverse transcriptase inhibitors (NRTIs)?
Nucleoside reverse transcriptase inhibitors (NRTIs) are antiviral drugs that mimic natural nucleosides and block viral DNA synthesis by inhibiting reverse transcriptase.
- They resemble normal DNA nucleosides (adenosine, guanosine, cytidine, thymidine analogs).
- After entering the host cell, they undergo three phosphorylation steps to become active.
- Once incorporated into viral DNA, they lack a 3′-OH group, causing chain termination.
3. What are nucleotide reverse transcriptase inhibitors (NtRTIs)?
Nucleotide reverse transcriptase inhibitors (NtRTIs) are antiviral drugs that mimic natural nucleotides and inhibit HIV reverse transcriptase after partial activation in the cell.
- They already contain one phosphate group.
- They require only two additional phosphorylation steps to become active.
- They are incorporated into viral DNA and cause DNA chain termination.
4. How do NRTIs and NtRTIs inhibit reverse transcriptase?
NRTIs and NtRTIs inhibit reverse transcriptase by acting as faulty nucleic acid building blocks that terminate viral DNA synthesis.
- They compete with natural deoxynucleotides.
- They are incorporated into the growing viral DNA strand.
- Because they lack a proper 3′-hydroxyl (3′-OH) group, no further nucleotides can be added.
5. Why do NRTIs require three phosphorylation steps?
NRTIs require three phosphorylation steps because they enter the cell as nucleoside analogs without any phosphate groups.
- First, a phosphate is added by a cellular kinase.
- Second and third phosphates are added sequentially.
- The final active form is a triphosphate, which can compete with natural nucleotides.
6. Why do nucleotide reverse transcriptase inhibitors require fewer activation steps?
NtRTIs require fewer activation steps because they already contain one phosphate group when administered.
- They are nucleotide analogs, not nucleosides.
- Only two additional phosphate groups need to be added.
- This can result in more efficient intracellular activation.
7. What is an example of a nucleoside reverse transcriptase inhibitor?
An example of a nucleoside reverse transcriptase inhibitor (NRTI) is zidovudine (AZT), one of the first drugs approved for HIV treatment.
- It is a thymidine analog.
- It undergoes three phosphorylation steps inside host cells.
- It causes termination of viral DNA during reverse transcription.
8. What is an example of a nucleotide reverse transcriptase inhibitor?
An example of a nucleotide reverse transcriptase inhibitor (NtRTI) is tenofovir, commonly used in HIV therapy and prevention.
- It is an adenosine monophosphate analog.
- It already contains one phosphate group.
- It inhibits reverse transcriptase by causing DNA chain termination.
9. Are NRTIs and NtRTIs used to treat HIV?
Yes, both NRTIs and NtRTIs are used as core components of antiretroviral therapy (ART) for HIV infection.
- They inhibit the viral enzyme reverse transcriptase.
- They prevent the formation of viral DNA from RNA.
- They are usually combined with other drug classes to prevent resistance.
10. How do NRTIs and NtRTIs cause DNA chain termination?
NRTIs and NtRTIs cause DNA chain termination because they lack the 3′-hydroxyl group required for phosphodiester bond formation.
- After incorporation into viral DNA, no new nucleotide can attach.
- This blocks elongation of the DNA strand.
- As a result, reverse transcription stops prematurely.
