Department of Chemical Sciences, Organic Mass Spectrometry Laboratory, University of Catania, Viale A. Doria 6, 95125 Catania, Italy.
Department of Biological, Geological and Environmental Sciences, Section of Molecular Biology, University of Catania, Viale A. Doria 6, 95125 Catania, Italy; National Institute for Biomembranes and Biosystems, Section of Catania, Viale A. Doria 6, 95125 Catania, Italy.
Biochim Biophys Acta Bioenerg. 2018 Sep;1859(9):806-816. doi: 10.1016/j.bbabio.2018.06.007. Epub 2018 Jun 8.
VDACs three isoforms (VDAC1, VDAC2, VDAC3) are integral proteins of the outer mitochondrial membrane whose primary function is to permit the communication and exchange of molecules related to the mitochondrial functions. We have recently reported about the peculiar over-oxidation of VDAC3 cysteines. In this work we have extended our analysis, performed by tryptic and chymotryptic proteolysis and UHPLC/High Resolution ESI-MS/MS, to the other two isoforms VDAC1 and VDAC2 from rat liver mitochondria, and we have been able to find also in these proteins over-oxidation of cysteines. Further PTM of cysteines as succination has been found, while the presence of selenocysteine was not detected. Unfortunately, a short sequence stretch containing one genetically encoded cysteine was not covered both in VDAC2 and in VDAC3, raising the suspect that more, unknown modifications of these proteins exist. Interestingly, cysteine over-oxidation appears to be an exclusive feature of VDACs, since it is not present in other transmembrane mitochondrial proteins eluted by hydroxyapatite. The assignment of a functional role to these modifications of VDACs will be a further step towards the full understanding of the roles of these proteins in the cell.
VDACs 有三种同工型（VDAC1、VDAC2、VDAC3），它们是线粒体外膜的整合蛋白，主要功能是允许与线粒体功能相关的分子进行通讯和交换。我们最近报道了 VDAC3 半胱氨酸的特殊过度氧化。在这项工作中，我们通过胰蛋白酶和糜蛋白酶水解以及 UHPLC/高分辨率 ESI-MS/MS 分析，将其扩展到来自大鼠肝线粒体的另外两种同工型 VDAC1 和 VDAC2，并且我们还能够在这些蛋白质中发现半胱氨酸的过度氧化。还发现了半胱氨酸的其他翻译后修饰，如琥珀酰化，而未检测到硒半胱氨酸的存在。不幸的是，一个包含一个遗传编码半胱氨酸的短序列片段在 VDAC2 和 VDAC3 中都没有被覆盖，这让人怀疑这些蛋白质存在更多未知的修饰。有趣的是，半胱氨酸过度氧化似乎是 VDACs 的特有特征，因为它不存在于通过羟基磷灰石洗脱的其他跨膜线粒体蛋白质中。这些 VDAC 修饰的功能作用的确定将是进一步全面了解这些蛋白质在细胞中的作用的一个步骤。
