How Does Helicase Unwind DNA? Helicase moves unidirectionally along the DNA, coupling the translocation with the local base pair separation. Therefore, the movement of helicase along DNA makes and breaks interactions with DNA. However, helicase mainly breaks hydrogen bonds between annealed nucleotide bases.
Helicase is an enzyme vital in unpacking double-stranded DNA. They are motor proteins that move unidirectionally along the phosphodiester backbone of the nucleic acid.
Key Areas Covered
1. What is Helicase
– Definition, Structure, Function
2. How Helicase Unwind DNA
– Mechanism of Action
Key Terms
Helicase, Unwind DNA
What is Helicase
Helicase is a class of enzymes that unpack double-stranded DNA. It is also a type of motor protein that moves directionally along the phosphodiester backbone of the nucleic acid. This, in turn, separates the hybridized nucleic acid strands. The enzyme helicase uses energy from ATP hydrolysis. Around 1% of the eukaryotic genes encode for helicases. In the human genome, there are 95 non-redundant helicases. Out of that, 64 helicases are RNA helicases, while 31 helicases are DNA helicases.
Figure 1: Helicase
Generally, the unpacking of nucleic acid is important for nucleic acid metabolism. Therefore, it is important in many cellular processes, including DNA replication, transcription, translation, DNA repair, recombination, and ribosome biogenesis. Normally, these processes involve the separation of nucleic acids. In addition, helicase uses the energy of ATP hydrolysis for the unwinding process. Therefore, helicases involve in the mechanical process of translocation, which in turn undergoes nucleic acid separation.
How Does Helicase Unwind DNA
Helicase is the enzyme that unwinds the double-stranded DNA into single strands as well as double-stranded RNA into single-stranded RNA to remove the secondary structures of RNA. Therefore, the main function of helicase is to undergo the separation of DNA double-helix or self-annealing RNA molecules using the energy from ATP hydrolysis. The main feature of the process is that it involves breaking hydrogen bonds between nucleotide bases that keep the double strand together. Helicases also help in the removal of nucleic-acid-associated proteins while catalyzing homologous DNA recombination.
Figure 2: Replication Fork
Furthermore, the movement of the helicase along the double-stranded DNA is directional, and the processivity depends on the type of helicase. Usually, DnaB-like helicases are responsible for the unwinding of DNA. They are ring-shaped hexamers. However, most of the other helicases are monomers or dimers. Normally, the processivity and the uncatalyzed unwinding are responsible for the displacement of strands.
However, the main characteristic feature of DNA helicases is that they unwind the DNA double-strand by breaking hydrogen bonds while removing the DNA-binding proteins from the DNA strands. In addition, the unwinding requires energy from ATP hydrolysis. Helicase moves directionally, breaking the hydrogen bonds and removing DNA-binding proteins to keep the different processes active. Apart from that, DnaB-like helicases are important during processes such as DNA replication. These helicases also occur in the replication fork during DNA replication. Some examples of metabolic processes that use helicases for unwinding DNA include ribosome biogenesis, transcription, translation, RNA splicing, RNA editing, RNA transport, and RNA degradation.
Conclusion
Helicase is an enzyme responsible for the unpacking of nucleic acids during nucleic acid metabolism. Usually, the main types of nucleic acid metabolism events include DNA replication, transcription, translation, ribosome biogenesis, RNA editing, RNA splicing, RNA transport, and RNA degradation. Helicases serve as motor proteins that are unidirectional. Meanwhile, helicases’ main function includes removing nucleic acid-binding proteins from the nucleic acid backbone and breaking the hydrogen bonds that keep the two nucleic acid strands together. Moreover, helicases require energy from ATP hydrolysis to carry out the process. DnaB is a hexameric helicase responsible for the unwinding of DNA strands. Therefore, it is the helicase that occurs in the replication fork during DNA replication.
References:
- “Helicase.” Wikipedia. Wikimedia Foundation.
Image Courtesy:
- “Helicase” By Phoebus87 at English Wikipedia – Own work (CC BY-SA 3.0) via Commons Wikimedia
- “DNA replication en” By LadyofHats Mariana Ruiz – Own Work (Public Domain) via Commons Wikimedia
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