Ristic Zoran, Momcilović Ivana, Fu Jianming, Callegari Eduardo, DeRidder Benjamin P
United States Department of Agriculture - Agricultural Research Service, Plant Science and Entomology Research Unit, 4008 Throckmorton Hall, Manhattan, KS 66506, USA.
J Plant Physiol. 2007 Dec;164(12):1564-71. doi: 10.1016/j.jplph.2007.07.008. Epub 2007 Sep 4.
Chloroplast protein synthesis elongation factor, EF-Tu, has been implicated in heat tolerance in maize. The recombinant precursor of this protein, pre-EF-Tu, has been found to exhibit chaperone activity and protect heat-labile proteins, such as citrate synthase and malate dehydrogenase, from thermal aggregation. Chloroplast EF-Tu is highly conserved and it is possible that the chaperone activity of this protein is not species-specific. In this study, we investigated the effect of native wheat pre-EF-Tu on thermal aggregation of rubisco activase. Additionally, we investigated the effect of native and recombinant maize pre-EF-Tu on activase aggregation. Activase was chosen because it displays an exceptional sensitivity to thermal aggregation and constrains photosynthesis at high temperature. The native precursors of both wheat and maize EF-Tu displayed chaperone activity, as shown by the capacity of both proteins to reduce thermal aggregation of rubisco activase in vitro. Similarly, the recombinant maize pre-EF-Tu protected activase from thermal aggregation. This is the first report on chaperone activity of native pre-EF-Tu and the first evidence for thermal protection of a photosynthetic enzyme by this putative chaperone. The results are consistent with the hypothesis that chloroplast EF-Tu plays a functional role in heat tolerance by acting as a molecular chaperone.
叶绿体蛋白质合成延伸因子EF-Tu与玉米的耐热性有关。已发现该蛋白的重组前体pre-EF-Tu具有伴侣活性，可保护柠檬酸合酶和苹果酸脱氢酶等热不稳定蛋白免受热聚集影响。叶绿体EF-Tu高度保守，该蛋白的伴侣活性可能不具有物种特异性。在本研究中，我们研究了天然小麦pre-EF-Tu对核酮糖-1,5-二磷酸羧化酶/加氧酶激活酶热聚集的影响。此外，我们还研究了天然和重组玉米pre-EF-Tu对激活酶聚集的影响。选择激活酶是因为它对热聚集表现出异常敏感性，并在高温下限制光合作用。小麦和玉米EF-Tu的天然前体均表现出伴侣活性，这两种蛋白在体外降低核酮糖-1,5-二磷酸羧化酶/加氧酶激活酶热聚集的能力表明了这一点。同样，重组玉米pre-EF-Tu保护激活酶免受热聚集影响。这是关于天然pre-EF-Tu伴侣活性的首次报道，也是这种假定伴侣对光合酶进行热保护的首个证据。这些结果与叶绿体EF-Tu作为分子伴侣在耐热性中发挥功能作用的假设一致。
