DNA-Binding Proteins: Overview & Application
Last updated on April 7, 2023 by
DNA-Binding Proteins: Overview
Proteins that have DNA-binding domains to bind single or double-stranded DNA are known as DNA-binding proteins.
These sequence-specific proteins contain functional groups that identify base pairs and allow them to interact with B-DNA’s major groove. However, there are also some DNA-binding ligands that interact with the minor groove of nucleic acid. These include netropsin, pentamidine, distamycin, and others.
Based on the functions the DNA-binding proteins perform, they are classified into four classes:
- Transcription factors: Involved in transcriptional regulation, such as transcription activators.
- DNA replications factors: Carry out in vivo and in vitro synthesis of whole genome or DNA fragments.
- Repair factors: Have a role in removing single base pairs or specific oligonucleotides and filling the gaps with suitable nucleotides. An example includes nucleases that cleave DNA molecules.
- Histones: Involved in transcription and chromosome packaging in the cell nucleus.
The DNA-binding motifs involved in forming a DNA complex include:
- Zinc finger: A small protein motif having a number of finger-like protrusions with one or more zinc ions (Zn2+) that bind to molecules, such as different proteins, lipids, DNA, or RNA substrates.
- Helix-turn-helix: Consists of two alpha helices joined by short amino acid strands. One helix of the protein is involved in DNA recognition. It binds to the major groove of DNA using hydrogen bonds and acts as a gene expression modulator. The other helix is involved in the stabilization of the DNA-protein complex.
- Leucine zipper: A common DNA-binding dimerization motif present in proteins. It consists of 60-80 amino acid sequences with diverse leucine zipper dimerization regions.
In this article, we will cover more about DNA-binding proteins, including their functions, working mechanisms, and industries that involve these sequence-specific proteins in lab workflows.
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How Do DNA-Binding Proteins Work?
DNA-binding proteins have the ability to recognize and bind to specific DNA sequences using different motifs. Typically, the protein binds to the major groove of DNA, although the minor groove is sometimes involved in the interactions. These protein-DNA interactions initiate a series of biochemical transitions that regulate all major biological functions in living cells.
An example of these interactions is transcription factors, a type of DNA-binding protein. They modulate the activation or repression of gene expression by binding to DNA motifs and histones that are part of the DNA skeleton.
DNA-Binding Proteins Interaction Types
The interaction of DNA-binding proteins with nucleic acid is of three types:
- Nonspecific DNA-protein interactions: One well-known example of this interaction is the bonding between DNA and structural proteins of chromosomes, such as histones in eukaryotes. These interactions help organize DNA into a compact structure called chromatin, which is crucial for the regulation of transcription.
Histones interact with double-stranded DNA through non-specific bonds, where its basic amino acid residues make ionic bonds with the acidic sugar-phosphate backbone of DNA.
The strength of this interaction can be affected by a chemical modification of these amino acid residues. This can then affect the transcription rate and DNA accessibility to transcription factors.
- Specific Protein and single-stranded DNA interactions: These proteins play a crucial role in the separation of the double helix of DNA into single strands during processes like DNA replication, repair, and recombination. Its example includes replication protein A. These proteins bind single-stranded DNA and stabilize it, preventing it from being degraded by nuclease or forming stem-loop structures.
- Specific DNA sequence binding: These are proteins that regulate transcription. They bind to specific DNA sequences near the promoter, leading to the activation or repression of genes.
What are DNA-Binding Proteins Used For?
DNA-binding proteins contain DNA-binding domains that carry out DNA-protein interaction. The DNA-protein complex performs different functions based on the type of complex formed between different DNA fragments and proteins. Some of them are involved in replication and recombination, while others are involved in transcription and DNA repair.
DNA replication is the process of synthesis of new DNA strands using older ones as a template. Unlike transcription factors, These proteins have non-sequence-specific DNA binding. They do not need a specific set of nucleotides to carry out their functions but work based on DNA structure. An example includes the DNA polymerase enzyme.
An exception to the case is the origin recognition complex (ORC) (in yeast) and dnaA (in Escherichia coli or E.coli). They specifically recognize origins and work in a sequence-specific fashion.
Transcription factors are the largest group of DNA-binding proteins. They control the transcription rate by binding to a specific sequence of DNA. They either regulate transcription alone or form complexes with different proteins. Its examples include activator or repressor proteins that guide RNA polymerase to specific genes for their activation or repression, and the hormone receptor family.
The transcription factors switch on and off the gene by binding to the promoter site, which either allows RNA polymerase to start transcription or prevents it from performing its functions.
DNA repair is the process of removing a damaged base pair or nucleotide sequence from the DNA and then filling the gap with the correct base pairs. They are crucial to repair occurring mutations in the genome of living organisms.
Based on the type of DNA damage repairs, DNA-binding proteins are classified into these groups: DNA mismatch repair, nucleotide excision repair, base excision repair, homologous recombination repair, and non-homologous end joining. Examples include DNA glycosylase, DNA polymerase I, and ligase.
Figure: The crystal structure of a human DNA-binding protein (Ku) to DNA (green).
What Industries Use DNA-Binding Proteins?
DNA-binding proteins have a range of functions in living cells, such as replication, packaging, rearrangement, transcription, gene regulation, recombination, and DNA repair.
We must examine the nature of protein-DNA complexes to understand how these processes work. And that’s why scientists in numerous fields of life science, including molecular biology, biochemistry, and biophysics, use engineered DNA-binding proteins to study the cellular processes of various organisms.
Engineered DNA-binding proteins, such as the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) (CRISPR/Cas) and transcription activator-like effector (TAL or TALE) proteins systems have been used for genome editing.
Other than altering genetic sequences they are also involved in vitro studies, such as transcriptional repression, chromatin modification, transcriptional activation, isolation of chromatin in a locus-specific manner, and visualization of genomic regions.
DNA-binding proteins have great potential applications in assays performed for the following agricultural purposes:
- Improving agricultural yields and quality
- Reducing the loss caused by biotic and abiotic stresses
- Boosting the utilization of germplasm resource
- Increasing breeding efficiency
- Heightening the regulation of plant growth
Engineered DNA-binding proteins act as scaffolds to create enzymes that can modify a DNA sequence, regulate transcription, or change the epigenetic status at any specific location within the genome.
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DNA-binding proteins are proteins having an affinity for different DNA molecules. They contain DNA-binding sites to recognize and bind specific DNA sequences to perform essential cellular processes, such as replication, recombination, and repair. Therefore, the engineered DNA-binding proteins are a crucial component of many life science lab assays.
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