Optimizing Enzymatic Photo-Redox Cycles by a Hybrid Protein Complex Chain

The construction from scratch of artificial cells by means of a "bottom up" approach is one of the most ambitious challenges in synthetic biology. Artificial cells capable of imitating the light phase of photosynthesis can be considered photoautotrophs. In bacterial photosynthesis, the first step in the light energy transduction process is the enzymatic photo-redox cycle catalysed by two membrane protein complexes, that is, the photosynthetic reaction centre (RC) and the ubiquinol oxidase (bc1(B)). In this work we studied this process in a micellar suspension of both proteins but coupling a bacterial RC with an ortholog bc1 extracted from mammalian mitochondria (bc1(M)). With this hybrid protein complex chain, the light transduction efficiency turns out to be enhanced up to 90 % by tuning the enzymatic level ratio of the two protein complexes. These results pave the way towards the reconstitution of the entire photosynthetic machinery in artificial membranes for the realization of photoautotrophic artificial cells.