Introduction - This script shows the structural modifications made to convert IGPS activity to PRAI activity. [Based on 1A53.pdb, 1IGS.pdb and the paper by Altamirano et al Nature 403 10 February 2000].

This is the complex of IGPS and its substrate, CdRP; note that the bound substrate is somewhat buried within the enzyme.

This view shows the TIM barrel of IGPS that forms the foundation for the construction of the new enzyme. Note the helices , beta sheets, and loops. The substrate, CdRP (grey) binds at one end of the central beta barrel.

One of the main differences between IGPS and PRAI is the 49 residue N-terminal extension of IGPS. This extension was deleted and the resultant protein dubbed IGPS49

The two other sites of greatest structure differentiation occur in loops b1a1 and b6a6, both of which control access to the active site and participate in the reaction. These loops were targeted for DNA shuffling to make them more similar to the b1a1 and b6a6 loops in PRAI.

After several rounds of selection, the resulting enzyme, in vitro evolved PRAI (ivePRAI), catalyzes the PRAI reaction despite being 90% homologous to the IGPS amino acid sequence. **NOTE: Cannot currently display ivePRAI pdb file in large window, sorry.**