We have examined the affinity of two recently synthesized flavin analogs for the isoalloxazine binding site of riboflavin-binding protein (RBP). The results showed that pyrimidopterines could bind to RBP [K(d) 160-250 μM]. This suggested that, at the FMN or FAD level, these analogs might also bind to other apoflavoproteins, thereby providing a high potential probe for flavin enzymology. In contrast, 4a,5-ring-opened isoalloxazines did not bind to RBP. However, 1,10a-ring-opened flavins bind with considerably avidity [K(d) about 40 nM]. Evidence is presented which indicates that the 4a,5-ring-opened species adopted a nonplanar configuration which, in turn, was responsible for the lack of affinity to RBP. Steric and electronic consequences of a 4a,5 ring opening are discussed in relation to flavin-dependent phenolic hydroxylases.
|Original language||English (US)|
|Number of pages||4|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Issue number||14 I|
|State||Published - 1984|
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