Difference Between Serine and Tyrosine Recombinase

The key difference between serine and tyrosine recombinase is that in serine recombinase, serine is the nucleophilic amino acid used by the enzyme to attack DNA during site-specific recombination, while in tyrosine recombinase, tyrosine is the nucleophilic amino acid used by the enzyme to attack the DNA during site-specific recombination.

Site-specific recombination (conservative site-specific recombination) is a type of genetic recombination technique where DNA strand exchange takes place between segments having a certain degree of sequence homology. Site-specific recombinases regulate the site-specific recombination process. These enzymes are grouped into two families as serine recombinase family and tyrosine recombinase family. The names come from the conserved nucleophilic amino acid residue present in the above two classes of recombinases which is used to attack DNA and which becomes covalently linked to it during strand exchange in site-specific recombination.

CONTENTS

1. Overview and Key Difference
2. What is Serine Recombinase
3. What is Tyrosine Recombinase
4. Similarities Between Serine and Tyrosine Recombinase
5. Side by Side Comparison – Serine vs Tyrosine Recombinase in Tabular Form
6. Summary

What is Serine Recombinase?

In the site-specific recombination method, two short DNA sequences (‘target sites’) are cut at specific points in both strands, and the cut ends are rejoined to new partners. Site-specific recombination technologies are genomic tools in genetic engineering that depend on recombinase enzymes to replace the target section of the DNA. Many site-specific recombination systems have been found to perform these DNA rearrangements for different purposes. But all these recombinase enzymes belong to two families. Serine recombinase is one of them. They can mediate up to three types of DNA rearrangements: integration, excision and inversion.

The site-specific recombinases like serine recombinase perform DNA rearrangement by recognising and binding to a short DNA sequence (target site), at which they cleave the DNA backbone. Later, the exchange of two DNA helices happens and rejoining of DNA strands takes place. In serine recombinase, serine is the amino acid that is used by the enzyme to attack the DNA during site-specific recombination. During DNA cleavage, the protein-DNA bond is formed via a transesterification reaction. The phosphodiester bond is replaced by the phosphoserine bond between the 5’phosphate group at the cleavage site and the hydroxyl group of a conserved serine residue. The new bond stores energy that expends in cleaving DNA at the target site. This energy is later used for rejoining the DNA to the corresponding deoxyribose hydroxyl group on the other site. Examples of serine recombinases are serine resolvases/invertases and serine integrases.

What is Tyrosine Recombinase?

Tyrosine recombinase is the other enzyme class that regulates conservative site-specific recombination. As described previously, tyrosine recombinase also carries out DNA rearrangement in the same manner by recognising and binding to a short DNA sequence (target site), at which they cleave DNA backbone. Later, exchanging of two DNA helices and rejoining of DNA strands take place.

But in tyrosine recombinase, tyrosine is the amino acid that is used by the enzyme to attack the DNA during site-specific recombination. The common feature of this class is a conserved nucleophilic tyrosine residue attacking the scissile DNA-phosphate to form a 3′-phosphotyrosine linkage. Tyrosine recombinases (A1) and tyrosine integrases (A2) are the prominent enzymes groups in the tyrosine recombinase enzyme family.

What are the Similarities Between Serine and Tyrosine Recombinase?

• They are a class of recombinase enzymes.
• Both regulate site-specific recombination.
• They are proteins.
• The basic chemical reaction is the same for both.
• Both catalyse transesterification reactions.

What is the Difference Between Serine and Tyrosine Recombinase?

In serine recombinase, serine is the nucleophilic amino acid that is used by the enzyme to attack the DNA during site-specific recombination. On the other hand, in tyrosine recombinase, tyrosine is the nucleophilic amino acid that is used by the enzyme to attack the DNA during site-specific recombination. So, this is the key difference between serine and tyrosine recombinase. The common feature of serine recombinase is that it forms a phosphoserine bond with DNA, while tyrosine recombinase forms a phosphotyrosine bond with DNA during the site-specific recombination process.

The below infographic lists the differences between serine and tyrosine recombinase in tabular form.

Summary – Serine vs Tyrosine Recombinase

Recombination can occur between similar molecules of DNA as in homologues recombination or dissimilar molecules as in non-homologues recombination. Site-specific recombination is a type of genetic recombination in which DNA strand exchanging takes place between segments having at least a certain degree of sequence homology. It is catalysed by recombinases. Most recombinases are grouped into two families: serine recombinase and tyrosine recombinase. Serine recombinase uses serine as the nucleophilic amino acid to attack the DNA during the site-specific recombination process. Tyrosine recombinase uses tyrosine as the nucleophilic amino acid to attack the DNA during the site-specific recombination process. Therefore, this is the key difference between serine and tyrosine recombinase.

Reference:

1. “Site-Specific Recombination.” Wikipedia, Wikimedia Foundation, 30 Dec. 2020, Available here.
2. Grindley, Nigel D.F. “Mechanisms of Site-Specific Recombination.” Annual Reviews, Available here.

Image Courtesy:

1. “SUrot” By Juergen Bode – Own work (CC BY-SA 3.0) via Commons Wikimedia

2. “STswap” By Juergen Bode – Own work (CC BY-SA 3.0) via Commons Wikimedia