<p>Flavodoxins are small redox-active proteins with a flavin mononucleotide (FMN) prosthetic group. They function as electron transfer agents in a variety of microbial metabolic processes, including nitrogen fixation by nitrogenase [<cite idref="PUB00014920"/>], sulphite reduction [<cite idref="PUB00014352"/>], and light-dependent NADP+ reduction during photosynthesis [<cite idref="PUB00014921"/>]. This entry describes the short chain type. Many of these are involved in sulphite reduction.</p>