Component of two multicomponent enzyme systems which are involved in the catabolism of naphthalene (PubMed:11872705, PubMed:9573207). Plays a role as an electron transfer component for both salicylate 5-hydroxylase (S5H) and naphthalene 1,2-dioxygenase (NDO) systems, by transferring electrons to the oxygenase components (PubMed:11872705, PubMed:9573207). Binds 1 [2Fe-2S] cluster per subunit. Aromatic compound metabolism; naphthalene degradation. Ferredoxin NagAb belongs to both the salicylate 5-hydroxylase (S5H) and the naphthalene 1,2-dioxygenase (NDO) multicomponent enzyme systems. The NDO multicomponent enzyme system is composed of an electron transfer component and a dioxygenase component (iron sulfur protein (ISP)). The electron transfer component is composed of a ferredoxin reductase (NagAa) and a ferredoxin (NagAb), and the dioxygenase component is formed by a large alpha subunit (NagAc) and a small beta subunit (NagAd). The S5H multicomponent enzyme system is composed of an electron transfer component and a monooxygenase component. The electron transfer component is composed of a ferredoxin reductase (NagAa) and a ferredoxin (NagAb), and the monooxygenase component is formed by a large subunit (NagG) and a small subunit (NagH). Cells lacking this gene are not able to convert salicylate to gentisate. Belongs to the bacterial ring-hydroxylating dioxygenase ferredoxin component family.