Amyloid-bound thioflavin T fluorescence was studied in lysates of yeast strains that carry mutations in the ADE1 or ADE2 genes and accumulate red pigment as a result of the polymerization of aminoimidazole ribotide (an intermediate of adenine biosynthesis). The fluorescence is drastically enhanced in cells grown in media with high concentrations of adenine (100 mg/l), which suppresses the accumulation of red pigment. Mutations that block the first stages of purine biosynthesis de novo also impede the accumulation of red pigment and produce the same effect on thioflavin fluorescence. Mutations in ADE1 or ADE2 genes in originally white prototrophic strains considerably suppress fluorescence. The fraction of protein polymers was studied by agarose gel electrophoresis, which permitted us to conclude that reduced fluorescence intensity was associated with decreased amyloid content in cells that accumulate red pigment. Model experiments with insulin fibers demonstrate that red pigment binds fibrils and blocks their interaction with thioflavin T. A comparison of lysate pellet proteins from red and white isogenic strains separated by 2D electrophoresis followed by MALDI analysis allowed us to identify 23 pigment-dependent proteins. These proteins mostly belong to functional classes of chaperones and proteins involved in glucose metabolism, which closely correspond to the prion-dependent proteins that we characterized previously. We suppose that the binding of red pigment with amyloid fibrils prevents the generation of prion aggregates and impedes prion propagation by blocking fibril contact with chaperones.