Department of Biological Sciences, Birla Institute of Science and Technology- K. K. Birla Goa Campus, Sancoale, Goa, India.
Plant Mol Biol. 2024 Aug 2;114(4):88. doi: 10.1007/s11103-024-01485-2.
Targeting heterologous multi-transmembrane domain (TMD) proteins to plant chloroplasts requires sequences in addition to the chloroplast transit peptide (cTP). The N-terminal domain (N-region), located C-terminal to the cTP in chloroplast inner envelope membrane proteins, is an essential region for import. However, it was unclear if the N-region functions solely as a spacer sequence to facilitate cTP access or if it plays an active role in the import process. This study addresses the N-region's role by using combinations of cTPs and N-regions from Arabidopsis chloroplast inner envelope membrane proteins to direct the cyanobacterial protein SbtA to the chloroplast. We find that the sequence context of the N-region affects the chloroplast import efficiency of SbtA, with particular sequences mis-targeting the protein to different cellular sub-compartments. Additionally, specific cTP and N-region pairs exhibit varying targeting efficiencies for different heterologous proteins. Substituting individual N-region motifs did not significantly alter the chloroplast targeting efficiency of a particular cTP and N-region pair. We conclude that the N-region exhibits contextual functioning and potentially functional redundancy in motifs.
靶向异源多跨膜结构域（TMD）蛋白到植物叶绿体需要除叶绿体转运肽（cTP）以外的序列。位于叶绿体内膜蛋白 cTP 羧基端的 N 端结构域（N 区）是导入所必需的区域。然而，N 区是否仅作为促进 cTP 进入的间隔序列起作用，还是在导入过程中发挥积极作用尚不清楚。本研究通过使用来自拟南芥叶绿体内膜蛋白的 cTP 和 N 区的组合，将蓝细菌蛋白 SbtA 定向到叶绿体，解决了 N 区的作用。我们发现 N 区的序列结构会影响 SbtA 的叶绿体导入效率，特定序列会将该蛋白错误靶向到不同的细胞亚区室。此外，特定的 cTP 和 N 区对不同的异源蛋白具有不同的靶向效率。替代单个 N 区基序不会显著改变特定 cTP 和 N 区对的叶绿体靶向效率。我们得出结论，N 区在基序中表现出上下文功能和潜在的功能冗余。
