Concurrent interactions of heme and FLU with Glu tRNA reductase (HEMA1), the target of metabolic feedback inhibition of tetrapyrrole biosynthesis, in dark- and light-grown Arabidopsis plants
Concurrent interactions of heme and FLU with Glu tRNA reductase (HEMA1), the target of metabolic feedback inhibition of tetrapyrrole biosynthesis, in dark- and light-grown Arabidopsis plants
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DOI：
10.1111/j.1365-313x.2004.02262.x
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发表时间：
2004-12-01
期刊：
影响因子：
7.2
通讯作者：
Apel, K
中科院分区：
文献类型：
--
作者：
Goslings, D;Meskauskiene, R;Apel, K
高等植物中四吡咯生物合成的调节归因于血红素对Glu tRNA还原酶的代谢反馈抑制。最近，又发现了四吡咯生物合成的另一个负调控因子，流感蛋白。在对突变的流感幼苗进行广泛的第二个位点筛选时，发现了一种流感抑制因子ulf3，它与hy1等位基因，并编码一种血红素加氧酶。Hy1突变体中血红素水平的增加与抑制Glu tRNA还原酶和抑制β-氨基酮戊酸(ALA)的合成和Pchlide积累有关。当与hy1或ulf3结合时，流感突变体中ALA合成的上调和原叶绿素的过度积累被严重抑制，支持了以下观点，即血红素通过抑制不依赖于流感的Glu tRNA还原酶来拮抗流感突变的影响。Glu tRNA还原酶C末端的螺旋卷曲结构域与Flu相互作用，而这种相互作用不需要Glu tRNA还原酶的N端位置，而这一位置是被血红素抑制酶所必需的。与Flu的相互作用是由HEMA1编码的Glu tRNA还原酶所特有的，该酶在光合作用活跃的组织中表达。流感似乎是第二个调控回路的一部分，该回路不仅在黄化的幼苗中，而且在适应光的绿色植物中，通过直接与Glu tRNA还原酶相互作用来控制叶绿素的生物合成。
The regulation of tetrapyrrole biosynthesis in higher plants has been attributed to metabolic feedback inhibition of Glu tRNA reductase by heme. Recently, another negative regulator of tetrapyrrole biosynthesis has been discovered, the FLU protein. During an extensive second site screen of mutagenized flu seedlings a suppressor of flu, ulf3, was identified that is allelic to hy1 and encodes a heme oxygenase. Increased levels of heme in the hy1 mutant have been implicated with inhibiting Glu tRNA reductase and suppressing the synthesis of delta-aminolevulinic acid (ALA) and Pchlide accumulation. When combined with hy1 or ulf3 upregulation of ALA synthesis and overaccumulation of protochlorophyllide in the flu mutants were severely suppressed supporting the notion that heme antagonizes the effect of the flu mutation by inhibiting Glu tRNA reductase independently of FLU. The coiled-coil domain at the C-terminal end of Glu tRNA reductase interacts with FLU, whereas the N-terminal site of Glu tRNA reductase that is necessary for the inhibition of the enzyme by heme is not required for this interaction. The interaction with FLU is specific for the Glu tRNA reductase encoded by HEMA1 that is expressed in photosynthetically active tissues. FLU seems to be part of a second regulatory circuit that controls chlorophyll biosynthesis by interacting directly with Glu tRNA reductase not only in etiolated seedlings but also in light-adapted green plants.