Chapter 3: Problem 6

What is the difference between type I and type II topoisomerases with respect to DNA cleavage?

Short Answer

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Question: Briefly explain the differences between type I and type II topoisomerases with respect to DNA cleavage. Answer: The main differences between type I and type II topoisomerases regarding DNA cleavage are: 1) type I topoisomerases cleave only one DNA strand (single-strand break), while type II topoisomerases cleave both DNA strands (double-strand break), 2) type I topoisomerases change the DNA linking number (Lk) in increments of one, while type II topoisomerases change the linking number in increments of two, and 3) type I topoisomerases do not require ATP for their function, whereas type II topoisomerases rely on ATP hydrolysis for their activity.

Step by step solution

Introduction to topoisomerases

Topoisomerases are enzymes that play a crucial role in DNA replication, transcription, and other cellular processes by regulating the topological state of DNA. They help in controlling DNA supercoiling and resolving tangles in the DNA structure. There are two main types of topoisomerases: type I and type II.

Understanding DNA cleavage

In the context of topoisomerases, DNA cleavage involves the breaking of one or both DNA strands to allow a change in the topology of the DNA molecule. After the required change in the DNA structure, the topoisomerases reseal the DNA strands by rejoining the broken ends.

Type I topoisomerases

Type I topoisomerases act by breaking one of the DNA strands (single-strand break) and, consequently, they change the DNA linking number (Lk) in increments of one. Type I topoisomerases do not require energy in the form of ATP to perform their function. The general reaction for type I topoisomerases is: TopoI-DNA complex \(\rightarrow\) Cleaved, covalently linked TopoI-DNA \(\rightarrow\) Relaxed, covalently linked TopoI-DNA \(\rightarrow\) Sealed, Relaxed DNA + TopoI

Type II topoisomerases

Type II topoisomerases, on the other hand, break both DNA strands (double-strand break), allowing another double-stranded DNA segment to pass through the gap before resealing the broken ends. As a result, type II topoisomerases change the DNA linking number (Lk) in increments of two. These enzymes utilize ATP hydrolysis to fuel their activity. The general reaction for type II topoisomerases is: TopoII-DNA complex \(\rightarrow\) Cleaved, covalently linked TopoII-DNA \(\rightarrow\) Strand passage, covalently linked TopoII-DNA \(\rightarrow\) Sealed, Relaxed DNA + TopoII + 2ADP + 2Pi

Differences in DNA cleavage between Type I and Type II topoisomerases

In summary, the primary differences between type I and type II topoisomerases with respect to DNA cleavage are: 1. Type I topoisomerases cleave only one DNA strand (single-strand break), whereas type II topoisomerases cleave both DNA strands (double-strand break). 2. Type I topoisomerases change the DNA linking number (Lk) in increments of one, whereas type II topoisomerases change the linking number in increments of two. 3. Type I topoisomerases do not require ATP for their function, while type II topoisomerases rely on ATP hydrolysis for their activity.

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What is the difference between type I and type II topoisomerases with respect to DNA cleavage?

Short Answer

Step by step solution

Introduction to topoisomerases

Understanding DNA cleavage

Type I topoisomerases

Type II topoisomerases

Differences in DNA cleavage between Type I and Type II topoisomerases

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