Positive selection of mutants defective in transcriptional repression of riboflavin synthesis by iron in the flavinogenic yeast Pichia guilliermondii.

It is known for many years that iron represses synthesis of riboflavin (RF) and most of RF-synthesizing enzymes in several yeast species, known as flavinogenic yeasts. However, the mechanism of such repression is not known. We have found that iron represses transcription of RIB1 and RIB7 genes coding for the first and the last enzymes of RF biosynthesis in the model flavinogenic organism Pichia guilliermondii.