Transferrins are iron binding transport proteins which bind Fe(3+) ion in association with the binding of an anion, usually bicarbonate. This transferrin binds only one Fe(3+) ion per protein molecule. Transports iron ions from the hemolymph into the eggs during the vitellogenic stage (oogenesis). Monomer. Not expressed in embryos. Maternal transferrin is used throughout embryogenesis. Belongs to the transferrin family.