Required for photosystem I (PSI) biosynthesis and assembly. May serve as a chloroplast scaffold protein that specifically assembles iron-sulfur (4Fe-4S) clusters and transfers them to the chloroplast PSI and ferredoxin-thioredoxin (FTR) complexes. Can assemble a 4Fe-4S cluster and transfer it to apoproteins in yeast cells. Probably not required for assembly or stability of plastidic 2Fe-2S clusters. Binds 1 [4Fe-4S] cluster. Expressed in aerial tissues exposed to light. Very low expression in roots. Seedling lethality when homozygous due to impaired photosystem I (PSI). Belongs to the Mrp/NBP35 ATP-binding proteins family.