Characterization of the plant uncoupling protein, SrUCPA, expressed in spadix mitochondria of the thermogenic skunk cabbage
Characterization of the plant uncoupling protein, SrUCPA, expressed in spadix mitochondria of the thermogenic skunk cabbage
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DOI：
10.1093/jxb/ern024
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发表时间：
2008-03-01
影响因子：
6.9
通讯作者：
Yamashita, Tetsuro
中科院分区：
文献类型：
--
作者：
Ito-Inaba, Yasuko;Hida, Yamato;Yamashita, Tetsuro
在哺乳动物棕色脂肪组织中，解偶联蛋白 1 (UCP1)（一种完整的线粒体内膜蛋白）会触发质子泄漏，并将由此产生的电子流产生的能量转化为热量。尽管最近在非产热组织中发现的植物 UCP 对其在生热作用中的参与提出了质疑，但对植物 UCP 在产热组织中的研究却很少。因此，在这项工作中，分析了从臭甘蓝产热花序中分离的两个克隆 UCP cDNA：SrUCPA 和 SrUCPB。 SrUCPA，而不是 SrUCPB，被确定为主要的解偶联蛋白，并且被发现整合到线粒体内膜中。拓扑分析表明，第一和第二基质内环对胰蛋白酶处理敏感，但第三基质内环对其具有抵抗力。使用肉穗花序线粒体，检查了 SrUCPA 的解偶联活性。尽管SrUCPA转录本在各种组织中组成型表达，而与产热阶段无关，但SrUCPA蛋白仅在产热组织或阶段中被检测到。另一方面，另一种产热蛋白 SrAOX 的基因和蛋白表达在产热组织或阶段特异性增加。定量免疫印迹分析表明，SrUCPA是肉穗花序线粒体中含量丰富的蛋白质，约占肉穗花序线粒体总蛋白的3%。结果表明，SrUCPA和SrAOX蛋白在生热组织或阶段的特异性共表达，以及SrUCPA蛋白在花序线粒体中的高表达，可能在臭菘的产热过程中发挥作用。
In mammalian brown adipose tissue, uncoupling protein 1 (UCP1), an integral inner mitochondrial membrane protein, triggers a proton leak and converts the energy generated by the resulting electron flow into heat. Although the recent finding of plant UCPs in non-thermogenic tissues has questioned their involvement in thermogenesis, there are few studies of plant UCPs in thermogenic tissues. Therefore, in this work, two cloned UCP cDNAs, SrUCPA and SrUCPB, isolated from the thermogenic spadix of skunk cabbage, were analysed. SrUCPA, not SrUCPB, was identified as the major uncoupling protein, and it was found to be integrated into the inner mitochondrial membrane. Topological analyses indicate that the 1st and 2nd intra-matrix loops are sensitive to trypsin treatment, but the 3rd intra-matrix loop is resistant to it. Using spadix mitochondria, the uncoupling activity of SrUCPA was examined. Although SrUCPA transcripts were constitutively expressed in various tissues irrespective of thermogenic stage, the SrUCPA protein was detected only in the thermogenic tissue or stage. On the other hand, both gene and protein expression for another heat-generating protein, SrAOX, were increased specifically in the thermogenic tissue or stage. Quantitative immunoblot analysis revealed that SrUCPA was an abundant protein in spadix mitochondria, accounting for about 3% of the total mitochondrial protein in the spadix. The results suggest that specific co-expression of SrUCPA and SrAOX protein in the thermogenic tissue or stage, as well as the high expression of SrUCPA protein in spadix mitochondria, may play a role in thermogenesis of skunk cabbage.