Gamma-tocopherol methyltransferase (γ-TMT) converts γ-toc to α-toc-the rate limiting step in toc biosynthesis. Sequencing results revealed that the coding regions of γ-TMT1 and γ-TMT3 were strongly similar to each other (93% at amino acid level). Based on the differences in the N-terminal amino acids, Glycine max-γ-TMT proteins are categorized into three isoforms: γ-TMT1, 2 and 3. In silico structural analysis revealed the presence of chloroplast transit peptide (cTP) in γ-TMT1 and γ-TMT3 protein. However, other properties of transit peptide like presence of hydrophobic amino acids at the first three positions of N-terminal end and lower level of acidic amino acids were revealed only in γ-TMT3 protein. Subcellular localization of GFP fused γ-TMT1 and γ-TMT3 under 35S promoter was studied in Nicotiana benthamiana using confocal microscopy. Results showed that γ-TMT1 was found in the cytosol and γ-TMT3 was found to be localized both in cytosol and chloroplast. Further the presence γ-TMT3 in chloroplast was validated by quantifying α-tocopherol through UPLC. Thus the present study of cytosolic localization of the both γ-TMT1 and γ-TMT3 proteins and chloroplastic localization of γ-TMT3 will help to reveal the importance of γ-TMT encoded α-toc in protecting both chloroplastic and cell membrane from plant oxidative stress.

中文翻译：

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烟草中最大甘氨酸γ-生育酚甲基转移酶亚型的亚细胞定位研究。

γ-生育酚甲基转移酶（γ-TMT）将γ-toc转化为α-toc，这是toc生物合成中的限速步骤。测序结果表明，γ-TMT1和γ-TMT3的编码区彼此非常相似（氨基酸水平为93％）。根据N末端氨基酸的差异，将Glycinemax-γ-TMT蛋白分为三种同工型：γ-TMT1、2和3。计算机模拟分析显示，γ-中存在叶绿体转运肽（cTP）。 TMT1和γ-TMT3蛋白。然而，仅在γ-TMT3蛋白中发现转运肽的其他特性，如在N末端的前三个位置存在疏水性氨基酸和酸性氨基酸水平较低。使用共聚焦显微镜研究了本氏烟草在35S启动子下GFP融合的γ-TMT1和γ-TMT3的亚细胞定位。结果表明，在细胞质中发现了γ-TMT1，在细胞质和叶绿体中都发现了γ-TMT3。此外，通过UPLC对α-生育酚进行定量，验证了叶绿体中γ-TMT3的存在。因此，目前对γ-TMT1和γ-TMT3蛋白的胞质定位以及γ-TMT3的叶绿体定位的研究将有助于揭示γ-TMT编码的α-toc在保护叶绿体和细胞膜免受植物氧化胁迫中的重要性。 。