Figure 3.

Insertion of one protein into another using circular permutation. (A) β-lactamase (BLA) was first permuted and then inserted into maltose binding protein (MBP), binding of maltose induces conformational changes that trigger hydrolysis of nitrocefin into a red product. Plating cells expressing the switch on β-lactam antibiotics allows engineering of probes responsive to ligands other that maltose; (B) Nitrocefin hydrolysis catalyzed by β-lactamase produces a red product; (C) Firefly luciferase engineered to detect cAMP. Binding of analyte to RIIβB promotes conformational change that increases bioluminescence.