An anti-CRISPR that pulls apart a CRISPR-Cas complex.

Area of Science:

• Molecular Biology
• Biochemistry

Background:

• Biological systems utilize protein inhibitors to regulate macromolecular complex activity.
• Anti-CRISPR proteins are a major class of inhibitors, with over 90 families identified, employing diverse inhibitory mechanisms.
• Existing inhibitors function via steric blocking, enzymatic modification, or perturbation of post-translational modifications.

Purpose of the Study:

• To characterize the anti-CRISPR protein AcrIF25.
• To elucidate the mechanism by which AcrIF25 inhibits the type I-F CRISPR-Cas system.

Main Methods:

• Structural and biochemical analyses were employed.
• The interaction of AcrIF25 with the CRISPR-Cas effector complex was investigated.

Main Results:

• AcrIF25 inhibits the type I-F CRISPR-Cas system by disassembling the effector complex.
• AcrIF25 binds to and removes Cas7 subunits from the CRISPR RNA sequentially, without enzymatic activity.
• This represents the first known protein to disassemble a large macromolecular complex without an external energy source.

Conclusions:

• AcrIF25 disassembles the type I-F CRISPR-Cas effector complex by sequentially removing Cas7 subunits.
• AcrIF25 functions without enzymatic activity, establishing a new paradigm for macromolecular complex inhibitors.
• This mechanism has potential biotechnological applications.