Redox signalling in the chloroplast: structure of oxidized pea fructose-1,6-bisphosphate phosphatase
Redox signalling in the chloroplast: structure of oxidized pea fructose-1,6-bisphosphate phosphatase
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DOI：
10.1093/emboj/18.23.6809
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发表时间：
1999-12-01
期刊：
影响因子：
11.4
通讯作者：
Cherfils, J
中科院分区：
文献类型：
--
作者：
Chiadmi, M;Navaza, A;Cherfils, J
阳光为光合作用同化二氧化碳提供了能量来源，但它也提供了调节信号，这些信号开启了参与叶绿体中光和暗代谢交替的特定酶组。叶绿素色素对光子的捕获触发氧化还原级联反应，最终通过硫氧还蛋白还原调节性二硫键来激活靶酶。在这里，我们报告的叶绿体果糖-1，6-二磷酸磷酸酶（FBPase）的氧化，低活性形式的结构，其中的四个酶的卡尔文循环的活动是由光氧化还原调节。该调节具有变构性质，二硫桥促进催化位点在20埃距离上的破坏。出乎意料的是，通过巯基-二硫键交换调节植物FBPases在各个方面都不同于通过AMP调节哺乳动物致突变FBEPases。我们还报道了氧化FBPase的第二种晶体形式，其四聚体结构明显偏离D-2对称性，这是寡聚体结构中的罕见事件，并且是组成型活性突变体的结构，其不能形成调节：二硫键。总之，这些结构为叶绿体中的氧化还原调节提供了结构基础。
Sunlight provides the energy source for the assimilation of carbon dioxide by photosynthesis, but it also provides regulatory signals that switch on specific sets of enzymes involved in the alternation of light and dark metabolisms in chloroplasts. Capture of photons by chlorophyll pigments triggers redox cascades that ultimately activate target enzymes via the reduction of regulatory disulfide bridges by thioredoxins. Here we report the structure of the oxidized, low-activity form of chloroplastic fructose-1,6-bisphosphate phosphatase (FBPase), one of the four enzymes of the Calvin cycle whose activity is redox-regulated by light. The regulation is of allosteric nature, with a disulfide bridge promoting the disruption of the catalytic site across a distance of 20 Angstrom. Unexpectedly, regulation of plant FBPases by thiol-disulfide interchange differs in every respect from the regulation of mammalian gluconeogenic FBEPases by AMP, We also report a second crystal form of oxidized FBPase whose tetrameric structure departs markedly from D-2 symmetry, a rare event in oligomeric structures, and the structure of a constitutively active mutant that is unable to form the regulatory: disulfide bridge. Altogether, these structures provide a structural basis for redox regulation in the chloroplast.