Fig. 1: Overview of ABE7.10.
From: Precise, minimally evolved adenine base editors generated through mutation reversion analysis
The ABE7.10 base editor is a fusion protein between nCas9 and the engineered deaminase TadA*7.10 (where TadA* indicates a mutated TadA variant). nCas9 and a user-supplied gRNA direct the editor to a region of interest, unwinding dsDNA to reveal a small window of accessible ssDNA on the non-target strand. The engineered TadA*7.10 acts on this substrate, converting adenosines to inosines, which are further processed to guanines, resulting in an overall A•T to G•C edit. Monomeric ABE7.10 was modeled in silico using ChimeraX, starting with the crystal structure of ABE8e (PDB ID: 6VPC) and replacing the catalytic TadA*8e domain with Alphafold2-predicted TadA*7.10. For simplicity, only the TadA domain and a short section of the ssDNA from the R-loop are shown (right). The residues that were mutated during the development of ABE7.10 are highlighted and color coded by the round of evolution they first emerged in. Relative stringencies for a given round of evolution were determined by kinetic pressure and number of selection targets used to evolve residues (left). Note that evolutionary rounds 4 and 6 did not produce any mutations that remained in the final iteration of ABE7.10.
