Rational engineering of sequence specificity in R.MwoI restriction endonuclease

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• R.MwoI is a Type II restriction enzyme recognizing a specific interrupted palindromic DNA sequence.
• It shares remote similarity with R.BglI, an enzyme with a known structure and a similar recognition motif.
• Understanding R.MwoI's mechanism is crucial for DNA manipulation and genetic engineering.

Purpose of the Study:

• To investigate the structural and functional basis of R.MwoI's DNA sequence recognition.
• To engineer R.MwoI variants with altered DNA sequence specificity.
• To demonstrate the feasibility of modifying restriction enzyme activity through targeted mutagenesis.

Main Methods:

• Construction of a homology model of R.MwoI complexed with DNA.
• Bioinformatics analysis to predict key amino acid residues involved in DNA recognition.
• Site-directed mutagenesis of the S310 residue in R.MwoI.
• Enzyme activity assays to determine the DNA sequence selectivity of wild-type and mutant enzymes.

Main Results:

• The homology model identified regions critical for recognizing common DNA bases shared by R.MwoI and R.BglI.
• Substitution of Serine 310 (S310) with Arginine (S310R) resulted in a variant recognizing the R.BglI target sequence (5'-GCCNNNNNGGC-3').
• The S310E variant exhibited altered selectivity, cleaving a subset of R.MwoI sites based on specific nucleotide identities.

Conclusions:

• A single amino acid substitution (S310) can significantly alter the DNA sequence specificity of R.MwoI.
• This study provides a model for engineering restriction enzymes based on structural homology and mutagenesis.
• The findings offer a practical approach for tailoring restriction enzymes for specific molecular biology applications.