Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden.
Plant Cell Physiol. 2009 Nov;50(11):1898-910. doi: 10.1093/pcp/pcp134. Epub 2009 Oct 14.
The TL29 protein is one of the more abundant proteins in the thylakoid lumen of plant chloroplasts. Based on its sequence homology to ascorbate peroxidases, but without any supporting biochemical evidence, TL29 was suggested to be involved in the plant defense system against reactive oxygen species and consequently renamed to APX4. Our in vivo and in vitro analyses failed to show any peroxidase activity associated with TL29; it bound neither heme nor ascorbate. Recombinant overexpressed TL29 had no ascorbate-dependent peroxidase activity, and various mutational analyses aiming to convert TL29 into an ascorbate peroxidase failed. Furthermore, in the thylakoid lumen no such activity could be associated with TL29 and, additionally, TL29 knock-out mutants did not show any decreased peroxidase activity or increased content of radical oxygen species when grown under light stress. Instead we could show that TL29 is a lumen-located component associated with PSII.
TL29 蛋白是植物叶绿体类囊体腔中含量较丰富的蛋白质之一。根据其与抗坏血酸过氧化物酶的序列同源性，但没有任何支持的生化证据，TL29 被认为参与植物防御系统对抗活性氧，因此被重新命名为 APX4。我们的体内和体外分析未能显示与 TL29 相关的任何过氧化物酶活性；它既不结合血红素也不结合抗坏血酸。重组过表达的 TL29 没有依赖抗坏血酸的过氧化物酶活性，并且各种旨在将 TL29 转化为抗坏血酸过氧化物酶的突变分析均以失败告终。此外，在类囊体腔中，TL29 与任何过氧化物酶活性都没有关联，而且，在光照胁迫下生长时，TL29 敲除突变体的过氧化物酶活性没有降低，活性氧的含量也没有增加。相反，我们可以证明 TL29 是一种与 PSII 相关的腔定位组件。
