8-Hydroxy-5-deazaflavin-dependent electron transfer in the extreme halophile Halobacterium cutirubrum

Cell extracts of the extreme halophile Halobacterium cutirubrum were found to contain 8-hydroxy-5-deazaflavin as well as 8-OH-5-deazaflavin: NADPH oxidoreductase activity. The oxidoreductase was partially purified and showed maximum activity at pH 5.4, which is unusually low for halobacteria, and 5.3 M NaCl, close to the intracellular salt concentration. The results indicate the presence of an 8-OH-5-deazaflavin-dependent electron transfer system in a nonmethanogenic organism.