Plays an important role in protecting the acceptor side of photosystem II (PSII) against oxidative damage, especially under iron-limiting growth conditions (Probable). The differing subcellular locations of futA1 (predominantly thylakoid lumen) and futA2 (predominantly periplasmic) suggest they may fulfill different roles. A major iron-binding protein involved in Fe(3+) uptake, probably part of a periplasmic ABC transporter complex futA1A2BC (TC 3.A.1.10.2) involved in Fe(3+) ion import (ferric iron). This protein and futA2 (slr0531) may be subunit proteins that have redundant or overlapping substrate-binding functions (Probable). Localization to the periplasm was not detected in PubMed:12368463. Transcript levels increase when cells are grown in the absence of iron. Protein levels increase when cells are grown in the absence of iron. Cells grow normally in the absence of iron but have a reduced capacity for Fe(3+) uptake; double knockouts of this gene and futA2 (slr0531) grow very poorly in the absence of iron and have a marked reduction in their ability to take up Fe(3+). Belongs to the bacterial solute-binding protein 1 family. There is controversy as to whether this protein preferentially binds Fe(2+) or Fe(3+), and also whether it is found associated with the plasma membrane or not.