Flavodoxins act in various electron-transport systems as functionalanalogues of ferredoxins [<cite idref="PUB00003573"/>]. Although flavodoxins are found onlyin certain bacteria and algae [<cite idref="PUB00000480"/>] the proteins share similaritywith a number of protein domains of both prokaryotic and eukaryotic origin [<cite idref="PUB00000282"/>].