Division of Plant Sciences and Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211-7310, USA.
Plant Cell Physiol. 2009 Nov;50(11):1923-32. doi: 10.1093/pcp/pcp136. Epub 2009 Oct 6.
Oligopeptide transporters (OPTs) are found in fungi, bacteria and plants. The nine Arabidopsis thaliana OPT genes are expressed mainly in the vasculature and are thought to transport tetra- and pentapeptides, and peptide-like substrates such as glutathione. Expression of AtOPT6 in Xenopus laevis oocytes demonstrated that AtOPT6 transports many tetra- and pentapeptides. In addition, AtOPT6 transported reduced glutathione (GSH), a tripeptide, but not oxidized glutathione (GSSG). Recent data showed that Candida albicans OPTs can transport peptides up to eight amino acids in length. AtOPT6 transported mammalian signaling peptides up to 10 amino acids in length and, in addition, known plant development- and nematode pathogenesis-associated peptides up to 13 amino acids long. AtOPT6 displayed high affinity for penta- and dodecapeptides, but low affinity for GSH. In comparison the Saccharomyces cerevisiae ScOPT1 was incapable of transporting any of the longer peptides tested. These data demonstrate the necessity of experimentally determining substrate specificity of individual OPTs, and lay a foundation for structure/function studies. Characterization of the AtOPT6 substrate range provides a basis for investigating the possible physiological function of AtOPT6 in peptide signaling and thiol transport in response to stress.
寡肽转运蛋白（OPTs）存在于真菌、细菌和植物中。拟南芥中的 9 种 OPT 基因主要在脉管系统中表达，被认为可以转运四肽和五肽，以及肽样底物，如谷胱甘肽。AtOPT6 在非洲爪蟾卵母细胞中的表达表明，AtOPT6 可以转运许多四肽和五肽。此外，AtOPT6 还转运还原型谷胱甘肽（GSH），一种三肽，但不转运氧化型谷胱甘肽（GSSG）。最近的数据表明，白色念珠菌 OPT 可以转运长达 8 个氨基酸的肽。AtOPT6 可以转运长达 10 个氨基酸的哺乳动物信号肽，此外，还可以转运已知的植物发育和线虫发病相关肽，长度可达 13 个氨基酸。AtOPT6 对五肽和十二肽具有高亲和力，但对 GSH 的亲和力较低。相比之下，酿酒酵母 ScOPT1 无法转运任何经过测试的较长肽。这些数据表明，有必要通过实验确定各个 OPT 的底物特异性，为结构/功能研究奠定基础。AtOPT6 底物范围的表征为研究 AtOPT6 在肽信号和应激响应中的硫醇转运中的可能生理功能提供了基础。
