The Pleiotropic Nature of rib80, hit1 , and red6 Mutations Affecting Riboflavin Biosynthesis in the Yeast Pichia guilliermondii

Abstract

The yeast Pichia guilliermondii is capable of riboflavin overproduction under iron deficiency. The rib80, hit1 , and red6 mutants of this species, which exhibit impaired riboflavin regulation, are also distinguished by increased iron concentrations in the cells and mitochondria, morphological changes in the mitochondria, as well as decreased growth rates (except for red6 ) and respiratory activity. With sufficient iron supply, the rib80 and red6 mutations cause a 1.5–1.8-fold decrease in the activity of such Fe–S cluster proteins as aconitase and flavocytochrome b2, whereas the hit1 mutation causes a six-fold decrease. Under iron deficiency, the activity of these enzymes was equally low in all of the studied strains.