Photolyase

Definition

Photolyase is an enzyme that utilizes light energy to repair DNA damage caused by ultraviolet (UV) radiation. This enzyme plays a critical role in the biological process of photoreactivation, where it specifically recognizes and reverses the formation of cyclobutane pyrimidine dimers in DNA, thus maintaining genomic stability.

5 Must Know Facts For Your Next Test

1. Photolyase is found in many organisms, including bacteria, plants, and animals, highlighting its evolutionary importance in protecting DNA from UV damage.
2. This enzyme is activated by blue or UV light, which provides the energy necessary for the repair process.
3. The structure of photolyase includes a chromophore that absorbs light and facilitates the repair reaction through a series of conformational changes.
4. In some organisms, photolyase can be repressed in the dark, demonstrating a dynamic response to environmental light conditions.
5. The efficiency of photolyase in repairing UV-induced damage can vary between species, influencing their adaptability to environments with high UV exposure.

Review Questions

• How does photolyase contribute to cellular protection against UV radiation?
  • Photolyase contributes to cellular protection against UV radiation by repairing DNA damage specifically caused by UV exposure. It recognizes cyclobutane pyrimidine dimers that form when UV light induces bonding between adjacent pyrimidines. By using light energy to reverse these lesions through the process of photoreactivation, photolyase helps maintain the integrity of the genome and prevents mutations that could lead to cellular dysfunction or disease.
• Discuss the role of photolyase in comparison to other DNA repair mechanisms.
  • Photolyase plays a unique role in DNA repair by specifically targeting UV-induced lesions through a light-dependent mechanism known as photoreactivation. Unlike nucleotide excision repair or base excision repair, which can operate in darkness and address various types of DNA damage, photolyase requires blue or UV light to function. This specialization allows organisms that possess photolyase to efficiently manage UV-induced damage while relying on other mechanisms for non-UV-related repairs.
• Evaluate the significance of photolyase's mechanism of action within the broader context of environmental adaptation for organisms exposed to high levels of UV radiation.
  • The mechanism of action of photolyase is significant for environmental adaptation as it allows organisms exposed to high levels of UV radiation to effectively repair DNA damage that could otherwise lead to detrimental mutations. The ability to harness light for this purpose showcases an evolutionary advantage in habitats like deserts or high altitudes where UV exposure is intense. Additionally, variations in the efficiency and presence of photolyase among different species can provide insights into their evolutionary strategies for coping with environmental stressors, highlighting its role in biodiversity and ecological resilience.

Related terms

Photoreactivation: A light-dependent DNA repair process in which photolyase binds to UV-induced DNA lesions and uses energy from light to cleave them.

Cyclobutane Pyrimidine Dimers (CPDs): DNA lesions formed when two adjacent pyrimidine bases covalently bond due to UV radiation, leading to distortion in the DNA structure.

DNA Repair Mechanisms: Biological processes that correct DNA damage, including base excision repair, nucleotide excision repair, and mismatch repair, in addition to photoreactivation.