The flavin reductase ActVB from Streptomyces coelicolor: characterization of the electron transferase activity of the flavoprotein form

TL;DR

This study characterizes the flavin reductase ActVB from Streptomyces coelicolor, revealing its dual role in electron transfer and iron reduction, which advances understanding of its enzymatic functions.

Contribution

It demonstrates that ActVB's FMN-bound form has ferric reductase activity, showing a dual role of FMN as substrate and cofactor in electron transfer.

Findings

FMN-bound ActVB exhibits ferric reductase activity

ActVB's active site has dual properties for FMN as substrate and cofactor

Enhances understanding of ActVB's role in actinorhodin biosynthesis

Abstract

The flavin reductase ActVB is involved in the last step of actinorhodin biosynthesis in Streptomyces coelicolor. Although ActVB can be isolated with some FMN bound, this form was not involved in the flavin reductase activity. By studying the ferric reductase activity of ActVB, we show that its FMN-bound form exhibits a proper enzymatic activity of reduction of iron complexes by NADH. This shows that ActVB active site exhibits a dual property with regard to the FMN. It can use it as a substrate that goes in and off the active site or as a cofactor to provide an electron transferase activity to the polypeptide.