Synthesis of chlorophyll-binding proteins in a fully-segregated ∆ycf54 strain of the cyanobacterium Synechocystis PCC 6803

The MS analysis is part of a wider study into chlorophyll biosynthesis. There is previous evidence, from both pulldown and CN-PAGE/immunoblot analyses that the enzyme Mg-protoporphyrin IX methylester cyclase (Cyc1), which catalyses the formation of the the fifth (E) ring in chlorophyll, associates with a protein of unknown function called Ycf54. There is also evidence for the association of Cyc1 with other enzymes in the chlorophyll biosynthetic pathway, eg. POR, ChlP and DVR. In the MS part of this study, FLAG-tagged Cyc1 was used to capture proteins from a Synechocystis cell lysate, with a comparison of FLAG-Cyc1 strains against wild-type and Ycf54 deletion backgrounds. MS-based quantification of the amounts of POR, ChlP and DVR relative to the Cyc1 bait supported evidence by immunoblotting of a significant reduction in these co-isolated proteins in the Ycf54 deletion strain.