Allosteric Mechanism in CRISPR–Cas 9

Anannya Roy, Amity University Kolkata

CRISPR stands for clustered regularly interspaced short palindromic repeats. Quite a mouthful isn’t it? In the name itself is hidden, its definition. It is composed of short identical palindromic DNA segments that are separated with spacer DNA, which are all unique. There are also a number of genes associated with CRISPR called Cas genes (CRISPR  associated genes) which produce cas proteins, mainly consisting of helicases and endonucleases.

Originally a defence mechanism employed by bacteria like Ecoli to protect themselves against the attack of bacteriophages has been modified in humans. A lot of research has been done on this, and this technology will revolutionize Medicine and Biotechnology. 

Allosterism is a property seen in many proteins and enzymes. It is a condition in which activity of a protein is altered as a consequence of the same molecule binding to a site than the active site. The molecule that binds is called the allosteric effector, and the binding can cause conformational changes in the enzyme’s structure affecting its affinity for the substrate.  This phenomenon is observed in the CRISPR-cas 9 system as well, affecting 3 main stages-

• DNA recognition
• Mediating cleavage
• Interfering with off-target activity

Under normal conditions, a Bacteriophage will infect a cell by injecting its genetic material which gets embedded into the genome of the host. But because of the CRISPR system, the viral DNA is cut as soon as it enters the cell. This is done by a complex formed of Cas9 and 2 RNAs- the CRISPR RNA (crRNA) that fits into the cas and the tracrRNA that holds the crRNA in place. Two RNAs together form what is called as the guide RNA.

Recently, molecular Dynamics stimulation was used to observe and understand the allosteric communication in CRISPR-cas 9. The ‘allosteric transducers’ were identified, and new variants of CRISPR-cas 9 could be developed that have improved specificity. This would be the future of gene editing, and a variety of diseases that mankind suffers from today can be cured and even easily prevented.

Also read:  Nanopores – As Single-Molecule Sensors

Citation-

Establishing the allosteric mechanism in CRISPR-Cas9  Łukasz Nierzwicki | Pablo Ricardo Arantes | Aakash Saha | Giulia Palermo https://onlinelibrary.wiley.com/doi/abs/10.1002/wcms.1503

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