DNA Gyrase presentation

BSM3201-1 MOLECULAR BIOLOGY

DNA GYRASE

TOPOISOMERASE II

DNA gyrase in bacteria (topoisomerase II in eukaryotes) relieves the tension by changing the DNA into negatively supercoiled DNA. How does it work？

Group 1:

• CHAI PEI HONG (211616)
• sharanya shree a/p subbarao (212651)
• toh xiao wei (213006)
• sabrina chowdhury diya (213745)

START

Introduction

Supercoiled

DNA GYRASE

If DNA Gyrase inhibited?

Mechanism

Differences between topoisomerase 1 & 2

INTRODUCTION

DNA Gyrase: - A type II topoisomerase - Found in the nucleoid region of bacterial cells- Involved in DNA replication and repair - Require 2 ATP molecules - Contain 3 gates: N-gates, DNA-gates, C-gates Function: - involved in the control of topological transitions of DNA- catalyse negative supercoiling (ATP- dependent

How E.Coli can packed so many DNA in its small volume?

Positive Supercoiling

Unseparated portion becomes more tightly woundOccur when the DNA strands relieves its helical stress by twisting around itself

+ Info

Mechanism of DNA Gyrase

Untangling the Knots: Exploring the Mechanism of Topoisomerase

Mechanism of DNA Gyrase

1. DNA gyrase binds to double-stranded DNA
2. Introduces a double-strand breaks
3. Another double-strand will pass through the gap
4. Reseals the double-strand break (require ATP)
5. The strands are releaved from DNA gyrase

Mechanism of DNA Gyrase

• It has the residue of tyrosine and one of the lone pairs of electrons on this oxygen of tyrosine acts as nucleophile and attacks the phosphorus
• Two electron bonds gets shifted on to this oxygen and an oxygen can pick up a hydrogen.
• It covalently bonds to the phosphorus thus breaking its phosphate sugar backbone

Differences between Topoisomerase I and Topoisomerase II

Topoisomerase II

Topoisomerase I

• Dimeric enzyme

(consists of two protein subunits)

• Enzyme which cut the both strands of double helix of DNA

(generate double-strand breaks)

• Monomeric enzyme

(consists of a single protein subunit)

• Enzyme which only cut one of the two strands of double helix of DNA

(generate single-strand breaks)

Differences between Topoisomerase I and Topoisomerase II

Topoisomerase II

Topoisomerase I

• Occurs in both eukaryotes and prokaryotes

• Require ATP hydrolysis

• Occurs in eukaryotes

• Does not require ATP hydrolysis

Topoisomerase Inhibition

Unraveling the power of topoisomerase inhibition: Breaking the chains of cancer growth

Inhibition Mechanism

Topoisomerases inhibitors act on both type 1 and 2

• Topoisomerase inhibition primarily occurs by the Inhibition of the religation reaction.

• This leads to the accumulation of DNA breaks, haulting DNA replication and causing apoptosis.

• The most important effect of these inhibitors is to block their target enzyme by binding to the active site, in the catalytic cycle where the enzyme is covalently bound to DNA. (Top-DNA cleavage complex)

Application

This inhibition mechanism provides key to drug development.Depending on the organism and type of topoisomerase being targeted; the inhibitors can work as :

Anti-bacterial agent

Fluoroquinolones are broad-spectrum potent anti-bacterial agents. The target these drugs are bacterial type 2 topoisomerase( DNA gyrase). Similarly, quinolones target both DNA gyrase and TOP IV

Chemotherapy

Anti-cancer agent

These drugs are now widely adminstered against lung cancer, ovarian cancer, testicular cancer and leukemia

Anthracyclins and podophyllotoxinsact as anti-cancer drugs specifically targeting TOP II. Whereas, Camptothecins inhibits TOP 1 activity. Both group of drugs work by preventing the re-sealing of DNA strands

REFERENCES

• Reece R. J., Maxwell A. (1991). DNA gyrase: Structure and function. Crit. Rev. Biochem. Mol. Biol. 26 335–375. 10.3109/10409239109114072
• Gore J, Bryant Z, Stone MD, Nollmann M, Cozzarelli NR, Bustamante C, "Mechanochemical Analysis of DNA Gyrase Using Rotor Bead Tracking", Nature 2006 Jan 5 (Vol. 439): 100-104.
• Sugino A, Cozzarelli NR (July 1980). "The intrinsic ATPase of DNA gyrase". The Journal of Biological Chemistry. 255 (13): 6299–306. doi:10.1016/S0021-9258(18)43737-4. PMID 6248518.
• Lakna. (2019). What is the difference between topoisomerase I and II? Retrieved from https://pediaa.com/what-is-the-difference-between-topoisomerase-i-and-ii/
• Kuroda, S., Kagawa, S., & Fujiwara, T. (2014). Selectively Replicating Oncolytic Adenoviruses Combined with Chemotherapy, Radiotherapy, or Molecular Targeted Therapy for Treatment of Human Cancers. Gene Therapy of Cancer (Third Edition), 171-183. https://doi.org/10.1016/B978-0-12-394295-1.00012-3
• Pommier, Y. (2008). Camptothecins. In: Offermanns, S., Rosenthal, W. (eds) Encyclopedia of Molecular Pharmacology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-38918-7_251
• Bardal, S. K., Waechter, J. E., & Martin, D. S. (2011). Neoplasia. Applied Pharmacology, 305-324. https://doi.org/10.1016/B978-1-4377-0310-8.00020-8

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