Structure of the Bacillus sphaericus R modification methylase gene

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The BspRI modification methylase gene from Bacillus sphaericus R was previously cloned into Escherichia coli.
• Understanding the gene's structure and function is crucial for molecular biology applications.

Purpose of the Study:

• To determine the nucleotide sequence of the BspRI methylase gene.
• To identify the gene's open reading frame, transcription start site, and translational initiation sites.
• To investigate the functional activity of proteins produced from different translational start sites.

Main Methods:

• DNA sequencing using the Maxam-Gilbert procedure.
• Subcloning experiments to map gene location and direction of transcription.
• In vitro transcription assays to localize the transcription initiation point.
• Protein synthesis studies in E. coli minicells.
• Analysis of Shine-Dalgarno sequences for translational initiation.

Main Results:

• A 2.5 kb DNA segment from B. sphaericus R contains the BspRI methylase gene.
• An open reading frame coding for a 424 amino acid protein (approx. 48 kDa) was identified.
• Transcription initiation and translational start sites were localized, with evidence for a secondary start site producing active methylase.
• The gene exhibits a strong preference for A.T base pairs and specific codon usage.

Conclusions:

• The complete nucleotide sequence and functional organization of the BspRI methylase gene have been elucidated.
• A shorter, functional methylase can be produced from a secondary translational start site.
• The gene's sequence and expression characteristics provide insights into DNA modification systems.