Fig. 5.

Resolving the consequences of FMAs using non-natural components. A similar workflow as for replacing the original variant by another natural variant (Fig. 4) is employed, except that, in the first step, the natural protein (left) is replaced by a functional non-natural protein from a library specifically designed for this purpose (middle). This can be achieved via homologous recombination (in the case of cyanobacterial or plastid transformation) or by complementation of a mutant that is grown heterotrophically (shown here). The function of the protein can be enhanced by laboratory evolution (right), optimizing interactions (from thin dotted lines to thick dotted lines) and involving adaptive sequence variation (indicated by altered shading) of the introduced non-natural protein and its binding partners