cexteins

Cexteins are a class of engineered protein scaffolds designed to serve as compact, stable frameworks for hosting catalytic or binding active sites. The concept arose in the field of protein engineering as an alternative to enzyme design, combining modularity with ease of production.

Typically cexteins are small proteins, commonly in the 40–120 amino acid range, that fold into compact structures such as alpha/beta barrels or beta-sheet motifs. They are designed to be tolerant to mutations and compatible with computational design and directed evolution.

Production is primarily by recombinant expression in Escherichia coli or yeast systems, with purification yielding high-stability variants. Advances in computational modeling and high-throughput screening have accelerated the creation of libraries of cextein variants to host catalytic or binding motifs.

Functions of cexteins include acting as enzyme mimics, scaffolds for artificial active sites, or binding modules in diagnostics. They are used in biosensors, therapeutic delivery platforms, and as components in modular nanomaterials. Their modularity enables swapping active sites without reengineering the entire scaffold.

Current challenges include achieving catalytic efficiencies comparable to natural enzymes, ensuring low immunogenicity for clinical applications, and scaling production. Research is active, with ongoing studies addressing design rules, stability under physiological conditions, and integration into larger systems.