A mobile tryptophan is the intrinsic charge transfer donor in a flavoenzyme essential for nikkomycin antibiotic biosynthesis.
A mobile tryptophan is the intrinsic charge transfer donor in a flavoenzyme essential for nikkomycin antibiotic biosynthesis.
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移动色氨酸是尼可霉素抗生素生物合成所必需的黄素酶中的内在电荷转移供体。
DOI：
10.1021/bi062087s
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发表时间：
2007
期刊：
影响因子：
2.9
通讯作者：
Jorns,MarilynSchuman
中科院分区：
文献类型：
--
作者：
Bruckner,RobertC;Zhao,Gouhua;Ferreira,Patricia;Jorns,MarilynSchuman
黄酶nikD是尼可霉素抗生素生物合成所必需的。NikD显示出一个不寻常的长波长吸收带，这归因于FAD与未知电荷转移供体的电荷转移复合物。NikD晶体含有内源性活性位点配体。在nikD提取物中检测到至少四种不同的化合物，包括可变量的两种ADP衍生物，其与FAD、吡啶甲酸盐（0.07 mol/mol nikD）和未知的吡啶甲酸盐样化合物竞争结合至酶的二核苷酸结合基序。生理催化反应的产物吡啶甲酸酯与nikD晶体中活性位点配体推导的性质相匹配。在将nikD与过量的吡啶甲酸酯混合时消除了电荷转移带，但不是通过除去吡啶甲酸酯样化合物的可逆解折叠程序，排除了两种化合物作为固有电荷转移供体。Trp 355突变为Phe消除了电荷转移带，伴随着底物结合亲和力降低30倍。结果为Trp 355作为本征电荷转移供体提供了明确的证据。Trp 355的吲哚环分别与nikD的“开放”或“封闭”结晶形式中的黄素环共面或垂直。重要的是，电荷转移相互作用需要共面构型。因此，在长波长区域的吸收构成了一个有价值的探针，用于监测溶液中的构象变化，这可能是重要的nikD催化。
The flavoenzyme nikD is required for the biosynthesis of nikkomycin antibiotics. NikD exhibits an unusual long wavelength absorption band attributed to a charge transfer complex of FAD with an unknown charge transfer donor. NikD crystals contain an endogenous active site ligand. At least four different compounds are detected in nikD extracts, including variable amounts of two ADP derivatives that bind to the enzyme's dinucleotide binding motif in competition with FAD, picolinate (0.07 mol/mol of nikD) and an unknown picolinate-like compound. Picolinate, the product of the physiological catalytic reaction, matches the properties deduced for the active site ligand in nikD crystals. The charge transfer band is eliminated upon mixing nikD with excess picolinate but not by a reversible unfolding procedure that removes the picolinate-like compound, ruling out both compounds as the intrinsic charge transfer donor. Mutation of Trp355 to Phe eliminates the charge transfer band, accompanied by a 30-fold decrease in substrate binding affinity. The results provide definitive evidence for Trp355 as the intrinsic charge transfer donor. The indole ring of Trp355 is coplanar with or perpendicular to the flavin ring in “open” or “closed” crystalline forms of nikD, respectively. Importantly, a coplanar configuration is required for charge transfer interaction. Absorption in the long wavelength region therefore constitutes a valuable probe for monitoring conformational changes in solution that are likely to be important in nikD catalysis.
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影响因子：
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作者：
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DOI：
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发表时间：
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影响因子：
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作者：
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