The role of Drosophila ninaG oxidoreductase in visual pigment chromophore biogenesis
The role of Drosophila ninaG oxidoreductase in visual pigment chromophore biogenesis
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DOI：
10.1074/jbc.m510293200
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发表时间：
2006-04-07
影响因子：
4.8
通讯作者：
O'Tousa, JE
中科院分区：
文献类型：
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作者：
Ahmad, ST;Joyce, MV;O'Tousa, JE
我们以前报道过（Sarfare，S.，艾哈迈德，S。T.，Joyce，M.五、博格斯，B.，和O'Tousa，J. E.（2005）J.Biol.Chem.280，11895-11901），果蝇ninaG基因编码参与作为Rh 1视紫红质发色团的（3S）-3-羟基视网膜的生物合成的氧化还原酶，并且表达Rh 4作为主要视蛋白的ninaG突变果蝇积累大量不同的类视色素。在这里，我们表明，这种未知的类维生素A是11-顺式-3-羟基视黄醇。与光电二极管阵列紫外-可见吸收检测器和质谱仪联用的反相高效液相色谱法显示，在保留时间t（r）为3.5 min处洗脱出主要产物，λ（max）类似于324 nm，质谱中的基峰为m/z 285。这些观察结果与3-羟基视黄醇标准品相同。电喷雾电离质谱中的基峰是由于离子源中的碎片化而从m/z 303处的质子化分子中损失水分子而产生的。这些结果表明，11-cis-3-hydroxyretinol是果蝇生色团生物合成所需的中间体。我们进一步表明，ninaG突变体喂养的视网膜作为维生素A的唯一来源，能够合成3-羟基类维生素A。因此，NinaG氧化还原酶不负责视网膜环的初始羟基化，而是在发色团产生的后续步骤中起作用。这些数据被用来审查生色团的生物合成，并提出NinaG在（3R）-3-羟基视黄醇转化为3S对映体的行为。
We previously reported (Sarfare, S., Ahmad, S. T., Joyce, M. V., Boggess, B., and O'Tousa, J. E. (2005) J. Biol. Chem. 280, 11895-11901) that the Drosophila ninaG gene encodes an oxidoreductase involved in the biosynthesis of the (3S)-3-hydroxyretinal serving as chromophore for Rh1 rhodopsin and that ninaG mutant flies expressing Rh4 as the major opsin accumulate large amounts of a different retinoid. Here, we show that this unknown retinoid is 11-cis-3-hydroxyretinol. Reversed phase high performance liquid chromatography coupled with a photodiode array UV-visible absorbance detector and mass spectrometer revealed a major product eluting at a retention time, t(r), of 3.5 min with a lambda(max) of similar to 324 nm and with a base peak in the mass spectrum at m/z 285. These observations are identical with those of the 3-hydroxyretinol standard. The base peak in the electrospray ionization mass spectrum arises from the loss of a water molecule from the protonated molecule at m/z 303 because of fragmentation in the ion source. These results suggest that 11-cis-3-hydroxyretinol is an intermediate required for chromophore biogenesis in Drosophila. We further show that ninaG mutants fed on retinal as the sole source of vitamin A are able to synthesize 3-hydroxyretinoids. Thus, the NinaG oxidoreductase is not responsible for the initial hydroxylation of the retinal ring but rather acts in a subsequent step in chromophore production. These data are used to review chromophore biosynthesis and propose that NinaG acts in the conversion of (3R)-3-hydroxyretinol to the 3S enantiomer.