User:Noroz6420/Flavodoxin

Flavodoxins are electron-transfer proteins. Flavodoxin is a bacterial protein that includes flavin mononucleotide. The structure of flavodoxin is characterized by a five-stranded parallel beta sheet, surrounded by alpha helices at either side of the sheet. They have been isolated from prokaryotes, cyanobacteria, and some eukaryotic algae.

Background
Originally found in cyanobacteria and clostridia, flavodoxins were discovered over 50 years ago. These proteins evolved from an anaerobic environment, due to selective pressures. Ferredoxin, another redox protein, was the only protein able to be used in this manner. However, when oxygen became present in the environment, iron became limited. Ferredoxin is iron-dependant as well as oxidant-sensitive. Under these limited iron conditions, ferredoxin was no longer preferred. Flavodoxin on the other hand is the opposite of these traits, as it is oxidant-resistant and has iron-free isofunctional counterparts. Therefore, for some time flavodoxin was the primary redox protein. Now however, when ferredoxin and flavodoxin are present in the same genome, ferredoxin is still used but under low iron conditions, flavodoxin is induced.

Structure
Flavodoxin proteins may consist of long or short chains. A long chain is determined when 20 amino acid residues are inserted into the last beta-strand. These residues form a loop which may be used to increase the binding affinity of flavin mononucleotide as well as assist in the formation of folded intermediates. However, it is still not certain what the loops true function is. In addition, the flavin mononucleotide is non-covalently bound to the flavodoxin protein and works to shuttle electrons.