BtsCI and BseGI display sequence preference in the nucleotides flanking the recognition sequence.

Area of Science:

• Molecular Biology
• Enzymology
• Biochemistry

Background:

• Restriction enzymes are crucial tools in molecular biology for DNA manipulation.
• The precise mechanism of target recognition and cleavage by restriction enzymes is not fully understood.
• Incomplete digestion of DNA hairpins by type II endonucleases BtsCI and BseGI was observed during oligonucleotide synthesis.

Purpose of the Study:

• To investigate the sequence-specific cleavage preferences of BtsCI and BseGI restriction enzymes.
• To understand the factors influencing the efficiency of DNA hairpin digestion by these enzymes.
• To elucidate the impact of sequence context and magnesium ion concentration on enzyme activity.

Main Methods:

• Synthesis of DNA hairpins with all possible dinucleotide combinations following the GGATG recognition site.
• Enzymatic digestion assays using BtsCI and BseGI.
• Kinetic analysis of enzyme activity and determination of rate constants.
• Assessment of cleavage efficiency in both hairpin and double-stranded DNA under varying Mg2+ concentrations.

Main Results:

• DNA hairpins containing adenine (A) immediately following the GGATG recognition site were digested more efficiently.
• This sequence preference was also observed in double-stranded DNA, particularly at higher Mg2+ concentrations.
• Kinetic studies revealed significant differences in catalytic rate constants for BtsCI across different sequences and between its two catalytic domains.
• Increased Mg2+ concentration decreased catalytic activity on the top strand, and this was not always coupled with a nick in the bottom strand.

Conclusions:

• BtsCI and BseGI exhibit a clear sequence preference for adenine at the +1 position after the GGATG recognition site, impacting DNA cleavage efficiency.
• Magnesium ion concentration plays a critical role in modulating the activity and cleavage fidelity of these enzymes, especially on the sense strand.
• Understanding these sequence and ionic preferences is essential for optimizing restriction enzyme applications in molecular biology, such as oligonucleotide synthesis.