Is the bacterial ferrous iron transporter FeoB a living fossil?

The cytoplasmic membrane protein FeoB of Escherichia coli, Helicobacter pylori, Legionella pneumophila and Synechocystis sp. strain PCC 6803 is necessary for Fe2+ uptake. The C-terminal part of FeoB is predicted to contain 8-12 membrane-spanning helices. The N-terminal domain shows much similarity to eukaryotic and prokaryotic G proteins and, indeed, GTPase activity is necessary for Fe2+ transport. Four of the five characteristic conserved G protein motifs have been identified in FeoB proteins. Whether FeoB is involved directly, via its Me2+ binding site, or indirectly in Fe2+ transport, remains to be investigated.