Debel K, Sierralta W D, Braun H P, Schmitz U K, Kloppstech K
Institut für Botanik, Universität Hannover, Germany.
Planta. 1997;201(3):326-33. doi: 10.1007/s004250050074.
The 23-kDa nuclear-encoded heat-shock protein (HSP) of Chenopodium rubrum L. is regulated by light at the posttranslational level. Higher light intensities are more effective in inducing the accumulation of the mature protein under heat-shock conditions. Based on this and other properties the protein was considered to belong to the group of small chloroplastic HSPs. However, we have now obtained the following evidence that this 23-kDa HSP is localized in the mitochondria: (i) Immunogold-labelled protein was almost exclusively restricted to the mitochondria in electron microscope thin sections. (ii) Using purified, isolated mitochondria from potato tubers the in-vitro-synthesized translation product of 31 kDa was readily transported into mitochondria where it was processed to the 23-kDa product. (iii) The protein could be detected by Western blotting in a preparation of washed mitochondria of Chenopodium, while under the same conditions no signal could be obtained in a preparation of isolated chloroplasts. (iv) Finally, sequence comparison with the published sequences of mitochondrial proteins by Lenne et al. (1995, Biochem J 311:805-813) and LaFayette et al. (1996, Plant Mol Biol 30:159-169) showed clearly that the 23-kDa protein is considerably more similar to these two proteins than to the group of plastid small HSPs. From these data we infer that mitochondria are involved in the response of the plants to high light stress under heat-shock conditions.
藜（Chenopodium rubrum L.）的23 kDa核编码热休克蛋白（HSP）在翻译后水平受光调控。在热休克条件下，较高的光照强度更有效地诱导成熟蛋白的积累。基于这一特性及其他特性，该蛋白被认为属于小型叶绿体HSPs家族。然而，我们现在获得了以下证据表明这种23 kDa HSP定位于线粒体中：（i）在电子显微镜超薄切片中，免疫金标记的蛋白几乎只局限于线粒体。（ii）使用从马铃薯块茎中纯化、分离的线粒体，体外合成的31 kDa翻译产物很容易转运到线粒体中，并在那里加工成23 kDa产物。（iii）通过蛋白质免疫印迹法可在藜洗涤过的线粒体提取物中检测到该蛋白，而在相同条件下，在分离的叶绿体提取物中未获得信号。（iv）最后，与Lenne等人（1995年，《生物化学杂志》311:805 - 813）和LaFayette等人（1996年，《植物分子生物学》30:159 - 169）发表的线粒体蛋白序列进行比较，结果清楚地表明，与质体小型HSPs家族相比，这种23 kDa蛋白与这两种蛋白的相似性更高。从这些数据我们推断，在热休克条件下，线粒体参与了植物对高光胁迫的响应。
