FokI requires two specific DNA sites for cleavage.

Area of Science:

• Molecular Biology
• Biochemistry
• Enzymology

Background:

• FokI is a type II restriction endonuclease known for its bipartite nature, recognizing a specific non-palindromic DNA sequence.
• Previous studies suggested FokI might function as a dimer, but the conditions and necessity for dimerization were not fully elucidated.
• Understanding the mechanism of restriction enzymes is key to their application in molecular biology and biotechnology.

Purpose of the Study:

• To investigate the dimerization behavior of the FokI restriction enzyme.
• To determine the role of divalent metal ions in FokI dimerization.
• To elucidate the structural requirements for FokI-mediated DNA cleavage and activation.

Main Methods:

• Dynamic light-scattering (DLS) was employed to assess protein aggregation and size.
• Gel-filtration chromatography was used to separate and analyze protein complexes based on size.
• Analytical ultracentrifugation provided detailed information on the mass and stoichiometry of FokI complexes.

Main Results:

• FokI was shown to dimerize exclusively in the presence of divalent metal ions.
• Analysis of the DNA-bound complex revealed the incorporation of two copies of the FokI recognition sequence.
• Dimer formation was demonstrated to be essential for the complete activation of FokI's cleavage function.

Conclusions:

• FokI dimerization is a metal ion-dependent process, critical for its enzymatic activity.
• The binding of two DNA recognition sites within a dimeric FokI complex is necessary for cleavage.
• These findings provide significant insights into the high-fidelity mechanism of monomeric type II restriction endonucleases.