Eliminating OFF-frame clones in randomized gene libraries: An improved split β-lactamase enrichment system

Area of Science:

• Biotechnology
• Molecular Biology
• Genetic Engineering

Background:

• Randomized libraries are crucial for biotechnological applications, but ensuring functional in-frame expression remains a challenge.
• Current methods often lack efficiency in selecting for functional diversity within large libraries.
• Genetic diversity is prioritized over ensuring correct gene expression, leading to potential loss of functional variants.

Purpose of the Study:

• To develop a faster and more efficient system for removing OFF-frame clones from randomized libraries.
• To increase the functional diversity of constructed libraries.
• To enable the construction of high-quality randomized libraries with a higher proportion of functional clones.

Main Methods:

• Utilized a split β-lactamase complementation system.
• Inserted the gene of interest between two fragments of the β-lactamase gene.
• Conferred β-lactam drug resistance only upon expression of an in-frame gene without stop codons or frameshifts.
• Developed a preinduction-free system for clone curation.

Main Results:

• The system efficiently eliminated OFF-frame clones, even from starting mixtures as low as 1% in-frame clones.
• Achieved enrichment of in-frame clones to approximately 70%, even with initial rates as low as 0.001%.
• Successfully applied the system to construct a single-domain antibody phage display library, maximizing functional diversity.

Conclusions:

• The split β-lactamase complementation system provides a robust and efficient method for curating randomized libraries.
• This approach significantly enhances the yield of functional clones, improving the overall quality and utility of libraries for biotechnological applications.
• The system is versatile and applicable to various library construction strategies, including antibody phage display.