School of Biological Sciences, College of Natural Sciences, Bangor University, Bangor LL57 2UW, United Kingdom.
J Plant Physiol. 2012 Nov 1;169(16):1631-8. doi: 10.1016/j.jplph.2012.05.026. Epub 2012 Aug 21.
Protein sequence analysis of a subfamily of 18 Arabidopsis acyl-activating enzymes (AAE) for organelle targeting signals revealed that eight of them possessed putative peroxisomal targeting signals (PTS1), five of which belonged to Clade VI of the AAE superfamily. Peroxisomal localization was confirmed by confocal microscopy of green fluorescent protein (GFP)-AAE fusion proteins co-localizing with peroxisomal RFP. The sequence analysis also revealed that all enzymes of Clade VI possess N-terminal regions indicative of chloroplast transit peptides (cTP). Among the five Clade VI peroxisomal enzymes tested, masking the PTS1 signal with GFP redirected three to plastids. In addition, three other peroxisomal AAEs appeared to be redirected to plastids in AAE-GFP fusion constructs. Due to the lack of evidence supporting plastid localization, we propose that competition dictates the exclusive localization to peroxisomes. AAE2 of Clade VI was the only enzyme with a putative mitochondrial targeting sequence, and it appeared to be targeted to mitochondria. The remainder of the AAEs appeared to be localized to plastids or cytosol. The AAE9-GFP fusion protein appeared to be located within discreet structures within plastids that may be plastoglobules. AAE15-GFP, but not AAE16-GFP appeared to be located in the chloroplast envelope. The number of examples is increasing whereby proteins located within other compartments contribute to plastid function. We provide an example of this through the light-sensitive phenotype of mutants of AAE2.
对拟南芥酰基辅酶 A 激活酶（AAE）的一个亚家族的 18 个蛋白序列进行分析，发现其中 8 个具有潜在的过氧化物酶体靶向信号（PTS1），其中 5 个属于 AAE 超家族的第六类。通过 GFP-AAE 融合蛋白与过氧化物酶体 RFP 的共定位，通过共焦显微镜证实了过氧化物酶体的定位。序列分析还表明，第六类的所有酶都具有叶绿体转运肽（cTP）的 N 端区域。在测试的五个第六类过氧化物酶体酶中，用 GFP 掩盖 PTS1 信号将三个酶重新定向到质体。此外，在 AAE-GFP 融合构建体中，另外三个过氧化物酶体 AAEs 似乎也被重新定向到质体。由于缺乏支持质体定位的证据，我们提出竞争决定了其对过氧化物体的专一性定位。第六类的 AAE2 是唯一具有潜在的线粒体靶向序列的酶，它似乎被靶向到线粒体。其余的 AAEs 似乎被定位到质体或细胞质。AAE9-GFP 融合蛋白似乎位于质体中的离散结构内，这些结构可能是质体小球体。AAE15-GFP，但不是 AAE16-GFP，似乎位于叶绿体被膜中。越来越多的例子表明，位于其他隔室的蛋白质有助于质体的功能。我们通过 AAE2 突变体的光敏感表型提供了一个这样的例子。
