Hacking the Photosynthetic Chain Using Phage Display Technique

H2 production in green algae is limited by the supply of electrons to the enzyme hydrogenase (HydA) since most of the electrons are redirected to a competing enzyme, ferredoxin-NADP+-reductase (FNR) for the assimilation of carbon dioxide by the Calvin Benson Bassham cycle. By strategically adhering HydA fusions to other photosynthetic proteins, it is possible to divert the electrons towards HydA. By applying phage display technology to produce a library of chimeric Hyd-peptites that bind to Cytb6f at diverse sites, we can discover electron access points that would otherwise have remained hidden using supervised approaches.
Moreover, we postulate that electron divergence hotspots will provide strategic positioning for enzymes catalyzing reductive processes, in our case, H2 production. We are applying peptides derived from phage display screen and fusing them to our model enzyme, HydA, to simultaneously identify new electron divergence hotspots and obtain the specific docking peptides to them. Due to its electrochemical properties, Cytb6f cannot donate electrons directly to HydA, however, by positioning HydA at a proximity to Cytb6f it may provide HydA with access to electrons from Fd during cyclic electron flow (CEF), thus, Fd might be able to reduce HydA. Not only can the electrons be "hijacked" from Fd towards HydA, the Cytb6f`s ability to perform CEF might be hindered. An impaired CEF fails to generate a proton motive force that drives the chloroplast’s ATP synthase to produce ATP. Thus, causing a partial inactivation of the CBB, and additional support to H2 production.