Required for the uptake of Fe(3+) ions. May participate in the transport of electrons from cytoplasm to an extracellular substrate (Fe(3+) ion) via FAD and heme intermediates (By similarity). Involved in iron homeostasis. 2 a Fe(II)-siderophore + H(+) + NAD(+) = 2 a Fe(III)-siderophore + NADH Expression decreased by the copper-sensing transcription factor MAC1.