Replacement of riboflavin by an analogue in the blue-light photoreceptor of Phycomyces

Abstract
Under suitable conditions, roseoflavin [7-methyl-8-dimethylamino-10-(1′-D-ribityl)isoalloxazine] replaces riboflavin to about 80% in the photoreceptor of Phycomyces . The substitute-bearing photoreceptor functions with an efficiency of about 0.1% of that of the normal receptor. The substitution is proven by ( i ) a decrease of the effective light flux by a factor of 4.7, expressed as a corresponding increase in threshold, and ( ii ) an increase of the effectiveness of 529-nm light relative to 380-nm light. It has also been shown that roseoflavin is taken up by the mycelium, translocated to the sporangiophore, and effectively phosphorylated by the riboflavin kinase of Phycomyces .