PMID:7918492
| Citation |
Raibekas, AA and Jorns, MS (1994) Affinity probing of flavin binding sites. 2. Identification of a reactive cysteine in the flavin domain of Escherichia coli DNA photolyase. Biochemistry 33:12656-64 |
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| Abstract |
8-(Methylsulfonyl)FAD reacts with a single cysteine residue (Cys293) in the flavin domain of Escherichia coli DNA photolyase to form an 8-(cysteinyl)FAD derivative covalently bound to the protein. About 80% protection against covalent attachment with 8-(methylsulfonyl)FAD was observed in the presence of an equimolar amount of FAD. Flavinylated photolyase retains the ability to repair pyrimidine dimers (15% of native activity) and to bind its antenna chromophore, 5,10-methenyltetrahydrofolate. Comparison of the properties of flavinylated enzyme with photolyase containing noncovalently bound 8-(methylthio)-FAD indicate that a perturbation is necessary to accommodate covalent bond formation. 8-(Methylthio)-FAD-reconstituted enzyme exhibits 95% of native activity. The aerobic stability of fully reduced and radical forms of 8-(methylthio)FAD enzyme is similar to that of native enzyme, whereas a radical form is not detected with flavinylated enzyme and the fully reduced enzyme is more easily oxidized by oxygen. The flavin in 8-(methylthio)FAD enzyme or flavinylated photolyase is shielded from solvent. However, the flavin environment in flavinylated enzyme is less hydrophobic as judged by spectral comparison with model 8-(alkylthio)flavins in various solvents. Enzyme containing noncovalently bound 8-(methylsulfonyl)-FAD was prepared by reconstitution with the fully reduced flavin which does not undergo covalent attachment. Covalent attachment was observed after reoxidation but probably involved dissociation and rebinding of oxidized 8-(methylsulfonyl)FAD. The results show that 8-(cysteinyl)FAD in flavinylated photolyase is at or near the normal flavin binding site.(ABSTRACT TRUNCATED AT 250 WORDS) |
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| Keywords |
Amino Acid Sequence; Binding Sites; Catalysis; Cysteine/metabolism; Deoxyribodipyrimidine Photo-Lyase/metabolism; Escherichia coli/enzymology; Flavin-Adenine Dinucleotide/analogs & derivatives; Flavin-Adenine Dinucleotide/metabolism; Molecular Sequence Data; Pyrimidine Dimers/metabolism; Tetrahydrofolates/metabolism |
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