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首页> 外文期刊>The FEBS journal >DNA binding and partial nucleoid localization of the chloroplast stromal enzyme ferredoxin : sulfite reductase
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DNA binding and partial nucleoid localization of the chloroplast stromal enzyme ferredoxin : sulfite reductase

机译：叶绿体基质酶铁氧还蛋白：亚硫酸盐还原酶的DNA结合和部分核苷定位

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Sulfite reductase (SiR) is an important enzyme catalyzing the reduction of sulfite to sulfide during sulfur assimilation in plants. This enzyme is localized in plastids, including chloroplasts, and uses ferredoxin as an electron donor. Ferredoxin-dependent SiR has been found in isolated chloroplast nucleoids, but its localization in vivo or in intact plastids has not been examined. Here, we report the DNA-binding properties of SiRs from pea (PsSiR) and maize (ZmSiR) using an enzymatically active holoenzyme with prosthetic groups. PsSiR binds to both double-stranded and single-stranded DNA without significant sequence specificity. DNA binding did not affect the enzymatic activity of PsSiR, suggesting that ferredoxin and sulfite are accessible to SiR molecules within the nucleoids. Comparison of PsSiR and ZmSiR suggests that ZmSiR does indeed have DNA-binding activity, as was reported previously, but the DNA affinity and DNA-compacting ability are higher in PsSiR than in ZmSiR. The tight compaction of nucleoids by PsSiR led to severe repression of transcription activity in pea nucleoids. Indirect immunofluorescence microscopy showed that the majority of SiR molecules colocalized with nucleoids in pea chloroplasts, whereas no particular localization to nucleoids was detected in maize chloroplasts. These results suggest that SiR plays an essential role in compacting nucleoids in plastids, but that the extent of association of SiR with nucleoids varies among plant species.
机译：亚硫酸还原酶（SiR）是一种重要的酶，可在植物吸收硫的过程中催化亚硫酸盐还原为硫化物。该酶位于包括叶绿体的质体中，并使用铁氧还蛋白作为电子供体。在分离的叶绿体核苷酸中发现了铁氧还蛋白依赖性的SiR，但尚未检查其在体内或完整质体中的定位。在这里，我们报告了使用带有修复基团的酶活性全酶从豌豆（PsSiR）和玉米（ZmSiR）的SiRs的DNA结合特性。 PsSiR结合到双链和单链DNA，而没有明显的序列特异性。 DNA结合不影响PsSiR的酶促活性，这表明铁氧还蛋白和亚硫酸盐可被核苷酸中的SiR分子接近。 PsSiR和ZmSiR的比较表明，ZmSiR确实具有DNA结合活性，如先前所报道的，但是PsSiR中的DNA亲和力和DNA压缩能力比ZmSiR高。 PsSiR对核仁的紧密压实导致豌豆核仁中转录活性的严重抑制。间接免疫荧光显微镜检查显示，大多数SiR分子与豌豆叶绿体中的类核苷酸共定位，而在玉米叶绿体中未检测到特定的类核苷酸定位。这些结果表明，SiR在压实质体中的核苷中起着至关重要的作用，但SiR与核苷的缔合程度因植物物种而异。

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