Kempiński Błażej, Chełstowska Anna, Poznański Jarosław, Król Kamil, Rymer Łukasz, Frydzińska Zuzanna, Girzalsky Wolfgang, Skoneczna Adrianna, Erdmann Ralf, Skoneczny Marek
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
Medizinische Fakultät, Biochemie und Pathobiochemie/Systembiochemie, Ruhr-Universität Bochum, Bochum, Germany.
Front Cell Dev Biol. 2020 Mar 27;8:198. doi: 10.3389/fcell.2020.00198. eCollection 2020.
The specificity of import of peroxisomal matrix proteins is dependent on the targeting signals encoded within their amino acid sequences. Two known import signals, peroxisomal targeting signal 1 (PTS1), positioned at the C-termini and PTS2 located close to N-termini of these proteins are recognized by the Pex5p and Pex7p receptors, respectively. However, in several yeast species, including , proteins exist that are efficiently imported into peroxisomes despite having neither PTS1 nor PTS2 and for which no other import signal has been determined. An example of such a protein is acyl-CoA oxidase (AOx) encoded by the gene. While it is known that its import is driven by its interaction with the N-terminal segment of Pex5p, which is separate from its C-terminal PTS1-recognizing tetratricopeptide domain, to date, no AOx polypeptide region has been implicated as critical for this interaction, and thus would constitute the long-sought PTS3 signal. Using random mutagenesis combined with a two-hybrid screen, we identified single amino acid residues within the AOx polypeptide that are crucial for this interaction and for the peroxisomal import of this protein. Interestingly, while scattered throughout the primary sequence, these amino acids come close to each other within two domains of the folded AOx. Although the role of one or both of these regions as the PTS3 signal is not finally proven, our data indicate that the signal guiding AOx into peroxisomal matrix is not a linear sequence but a signal patch.
过氧化物酶体基质蛋白的输入特异性取决于其氨基酸序列中编码的靶向信号。两种已知的输入信号，即位于这些蛋白质C末端的过氧化物酶体靶向信号1（PTS1）和靠近N末端的PTS2，分别被Pex5p和Pex7p受体识别。然而，在包括酿酒酵母在内的几种酵母物种中，存在一些蛋白质，尽管既没有PTS1也没有PTS2，但仍能有效地输入过氧化物酶体，并且尚未确定其他输入信号。这样一种蛋白质的例子是由POX1基因编码的酰基辅酶A氧化酶（AOx）。虽然已知其输入是由它与Pex5p的N末端片段的相互作用驱动的，该片段与其C末端识别PTS1的四肽重复结构域是分开的，但迄今为止，尚未发现AOx多肽区域对这种相互作用至关重要，因此将构成长期寻找的PTS3信号。通过随机诱变结合双杂交筛选，我们确定了AOx多肽内对这种相互作用和该蛋白质的过氧化物酶体输入至关重要的单个氨基酸残基。有趣的是，虽然这些氨基酸分散在一级序列中，但在折叠的AOx的两个结构域内彼此靠近。虽然这两个区域中的一个或两个作为PTS3信号的作用尚未最终得到证实，但我们的数据表明，引导AOx进入过氧化物酶体基质的信号不是线性序列，而是信号斑。
