Yeast flavohemoglobin protects against nitrosative stress and controls ferric reductase activity.

The role of Saccharomyces cerevisiae flavohemoglobin (Yhb1) is controversial and far from understood. This study compares the effects of nitrosative and oxidative challenge on the yeast mutant lacking the YHB1 gene. Growth of the mutant was impaired by nitrosoglutathione and peroxynitrite, whereas increased sensitivity to reactive oxygen species was not observed. Increased levels of intracellular NO(*) after incubation with NO(*) donors were found in the mutants cells as compared to the wild-type cells. Deletion of the YHB1 gene was found to augment the reduction of Fe(3+) by yeast cells which suggests that flavohemoglobin participates in regulation of the activity of plasma membrane ferric reductase(s).