Dpto, de Fisiología Vegetal, Centro Hispano Luso de Investigaciones Agrarias (CIALE), Universidad de Salamanca, Plaza Doctores de la Reina s/n, Campus Miguel Unamuno, Salamanca, 37007, Spain.
BMC Plant Biol. 2012 Nov 7;12:207. doi: 10.1186/1471-2229-12-207.
Many proteins with tandem repeats in their sequence have been described and classified according to the length of the repeats: I) Repeats of short oligopeptides (from 2 to 20 amino acids), including structural cell wall proteins and arabinogalactan proteins. II) Repeats that range in length from 20 to 40 residues, including proteins with a well-established three-dimensional structure often involved in mediating protein-protein interactions. (III) Longer repeats in the order of 100 amino acids that constitute structurally and functionally independent units. Here we analyse ShooT specific (ST) proteins, a family of proteins with tandem repeats of unknown function that were first found in Leguminosae, and their possible similarities to other proteins with tandem repeats.
ST protein sequences were only found in dicotyledonous plants, limited to several plant families, mainly the Fabaceae and the Asteraceae. ST mRNAs accumulate mainly in the roots and under biotic interactions. Most ST proteins have one or several Domain(s) of Unknown Function 2775 (DUF2775). All deduced ST proteins have a signal peptide, indicating that these proteins enter the secretory pathway, and the mature proteins have tandem repeat oligopeptides that share a hexapeptide (E/D)FEPRP followed by 4 partially conserved amino acids, which could determine a putative N-glycosylation signal, and a fully conserved tyrosine. In a phylogenetic tree, the sequences clade according to taxonomic group. A possible involvement in symbiosis and abiotic stress as well as in plant cell elongation is suggested, although different STs could play different roles in plant development.
We describe a new family of proteins called ST whose presence is limited to the plant kingdom, specifically to a few families of dicotyledonous plants. They present 20 to 40 amino acid tandem repeat sequences with different characteristics (signal peptide, DUF2775 domain, conservative repeat regions) from the described group of 20 to 40 amino acid tandem repeat proteins and also from known cell wall proteins with repeat sequences. Several putative roles in plant physiology can be inferred from the characteristics found.
许多序列中具有串联重复的蛋白质已根据重复的长度进行了描述和分类：I）短寡肽（2 到 20 个氨基酸）的重复，包括结构细胞壁蛋白和阿拉伯半乳聚糖蛋白。II）长度在 20 到 40 个残基之间的重复，包括具有明确三维结构的蛋白质，这些蛋白质通常参与介导蛋白质-蛋白质相互作用。III）长度在 100 个氨基酸左右的更长重复，构成结构和功能独立的单元。在这里，我们分析了 ShooT 特异（ST）蛋白，这是一类具有串联重复但功能未知的蛋白质，最初在豆科植物中发现，它们可能与其他具有串联重复的蛋白质有相似之处。
ST 蛋白序列仅在双子叶植物中发现，仅限于几个植物科，主要是豆科和菊科。STmRNA 主要在根部积累，并在生物相互作用下积累。大多数 ST 蛋白具有一个或多个未知功能域 2775（DUF2775）。所有推断的 ST 蛋白都有一个信号肽，表明这些蛋白质进入分泌途径，成熟的蛋白质具有串联重复的寡肽，它们共享一个六肽（E/D）FEPRP，后面跟着 4 个部分保守的氨基酸，这可能决定了一个潜在的 N-糖基化信号和一个完全保守的酪氨酸。在系统发育树中，序列根据分类群聚类。暗示可能参与共生和非生物胁迫以及植物细胞伸长，尽管不同的 ST 可能在植物发育中发挥不同的作用。
我们描述了一个称为 ST 的新蛋白质家族，其存在仅限于植物界，特别是仅限于少数双子叶植物科。它们具有 20 到 40 个氨基酸的串联重复序列，与描述的 20 到 40 个氨基酸串联重复蛋白组以及具有重复序列的已知细胞壁蛋白具有不同的特征（信号肽、DUF2775 结构域、保守重复区）。从发现的特征可以推断出几种在植物生理学中可能的作用。
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