Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.
J Struct Biol. 2011 Oct;176(1):24-31. doi: 10.1016/j.jsb.2011.07.004. Epub 2011 Jul 21.
TL29 is a plant-specific protein found in the thylakoid lumen of chloroplasts. Despite the putative requirement in plants for a peroxidase close to the site of photosynthetic oxygen production, and the sequence homology of TL29 to ascorbate peroxidases, so far biochemical methods have not shown this enzyme to possess peroxidase activity. Here we report the three-dimensional X-ray crystal structure of recombinant TL29 from Arabidopsis thaliana at a resolution of 2.5Å. The overall structure of TL29 is mainly alpha helical with six longer and six shorter helical segments. The TL29 structure resembles that of typical ascorbate peroxidases, however, crucial differences were found in regions that would be important for heme and ascorbate binding. Such differences suggest it to be highly unlikely that TL29 functions as a peroxidase.
TL29 是一种植物特异性蛋白，存在于叶绿体类囊体腔中。尽管植物中可能需要一种靠近光合氧产生部位的过氧化物酶，并且 TL29 与抗坏血酸过氧化物酶具有序列同源性，但迄今为止，生化方法并未表明该酶具有过氧化物酶活性。在这里，我们报道了来自拟南芥的重组 TL29 的三维 X 射线晶体结构，分辨率为 2.5Å。TL29 的整体结构主要为α螺旋，有六个较长的和六个较短的螺旋段。TL29 结构类似于典型的抗坏血酸过氧化物酶，但在对血红素和抗坏血酸结合很重要的区域发现了关键差异。这些差异表明 TL29 极不可能作为过氧化物酶发挥作用。
