There is a group of proteins that are encoded by a single gene, expressed as a single precursor protein and dually targeted to both mitochondria and chloroplasts using an ambiguous targeting peptide. Sequence analysis...There is a group of proteins that are encoded by a single gene, expressed as a single precursor protein and dually targeted to both mitochondria and chloroplasts using an ambiguous targeting peptide. Sequence analysis of 43 dual targeted proteins in comparison with 385 mitochondrial proteins and 567 chloroplast proteins ofArabidopsis thaliana revealed an overall significant increase in phenylalanines, leucines, and serines and a decrease in acidic amino acids and glycine in dual targeting peptides （dTPs）. The N-terminal portion of dTPs has significantly more serines than mTPs. The number of arginines is similar to those in mTPs, but almost twice as high as those in cTPs. We have investigated targeting determinants of the dual targeting peptide of Thr-tRNA synthetase （ThrRS-dTP） studying organellar import of N- and C-terminal deletion constructs of ThrRS-dTP coupled to GFR These results show that the 23 amino acid long N-terminal portion of ThrRS-dTP is crucial but not sufficient for the organellar import. The C-terminal deletions revealed that the shortest peptide that was capable of conferring dual targeting was 60 amino acids long. We have purified the ThrRS- dTP（2-60） to homogeneity after its expression as a fusion construct with GST followed by CNBr cleavage and ion exchange chromatography. The purified ThrRS-dTP（2-60） inhibited import of pF1β into mitochondria and of pSSU into chloroplasts at μM concentrations showing that dual and organelle-specific proteins use the same organellar import pathways. Furthermore, the CD spectra of ThrRS-dTP（2-60） indicated that the peptide has the propensity for forming α-helical structure in membrane mimetic environments; however, the membrane charge was not important for the amount of induced helical structure. This is the first study in which a dual targeting peptide has been purified and investigated by biochemical and biophysical means.展开更多
成人T细胞白血病(Adult T-cell leukemia,ATL)是与人类T淋巴细胞白血病1型病毒(Human T-cell leukemia virus type 1,HTLV-1)感染密切相关的恶性淋巴细胞白血病.HTLV-1反义编码的HBZ(HTLV-1 b ZIP factor)蛋白在ATL发生过程中扮演极为...成人T细胞白血病(Adult T-cell leukemia,ATL)是与人类T淋巴细胞白血病1型病毒(Human T-cell leukemia virus type 1,HTLV-1)感染密切相关的恶性淋巴细胞白血病.HTLV-1反义编码的HBZ(HTLV-1 b ZIP factor)蛋白在ATL发生过程中扮演极为重要的角色.为了寻找治疗成人T细胞白血病的方法,设计了能与HBZ蛋白形成二聚体,从而封闭HBZ蛋白功能的靶向多肽R8-HBAP.通过免疫共沉淀实验,发现R8-HBAP可以有效抑制HBZ蛋白与下游靶蛋白c-Jun的结合,报告基因实验显示,R8-HBAP能阻遏HBZ蛋白对AP-1信号通路的调控作用.MTT和流式细胞术实验发现,R8-HBAP能抑制ATL细胞的恶性增殖并促进细胞凋亡.因此,靶向多肽R8-HBAP通过阻遏HBZ蛋白的功能从而抑制白血病细胞的恶性增殖,为R8-HBAP的开发利用及成人T细胞白血病的治疗提供一定的实验依据.展开更多
文摘There is a group of proteins that are encoded by a single gene, expressed as a single precursor protein and dually targeted to both mitochondria and chloroplasts using an ambiguous targeting peptide. Sequence analysis of 43 dual targeted proteins in comparison with 385 mitochondrial proteins and 567 chloroplast proteins ofArabidopsis thaliana revealed an overall significant increase in phenylalanines, leucines, and serines and a decrease in acidic amino acids and glycine in dual targeting peptides （dTPs）. The N-terminal portion of dTPs has significantly more serines than mTPs. The number of arginines is similar to those in mTPs, but almost twice as high as those in cTPs. We have investigated targeting determinants of the dual targeting peptide of Thr-tRNA synthetase （ThrRS-dTP） studying organellar import of N- and C-terminal deletion constructs of ThrRS-dTP coupled to GFR These results show that the 23 amino acid long N-terminal portion of ThrRS-dTP is crucial but not sufficient for the organellar import. The C-terminal deletions revealed that the shortest peptide that was capable of conferring dual targeting was 60 amino acids long. We have purified the ThrRS- dTP（2-60） to homogeneity after its expression as a fusion construct with GST followed by CNBr cleavage and ion exchange chromatography. The purified ThrRS-dTP（2-60） inhibited import of pF1β into mitochondria and of pSSU into chloroplasts at μM concentrations showing that dual and organelle-specific proteins use the same organellar import pathways. Furthermore, the CD spectra of ThrRS-dTP（2-60） indicated that the peptide has the propensity for forming α-helical structure in membrane mimetic environments; however, the membrane charge was not important for the amount of induced helical structure. This is the first study in which a dual targeting peptide has been purified and investigated by biochemical and biophysical means.
文摘成人T细胞白血病(Adult T-cell leukemia,ATL)是与人类T淋巴细胞白血病1型病毒(Human T-cell leukemia virus type 1,HTLV-1)感染密切相关的恶性淋巴细胞白血病.HTLV-1反义编码的HBZ(HTLV-1 b ZIP factor)蛋白在ATL发生过程中扮演极为重要的角色.为了寻找治疗成人T细胞白血病的方法,设计了能与HBZ蛋白形成二聚体,从而封闭HBZ蛋白功能的靶向多肽R8-HBAP.通过免疫共沉淀实验,发现R8-HBAP可以有效抑制HBZ蛋白与下游靶蛋白c-Jun的结合,报告基因实验显示,R8-HBAP能阻遏HBZ蛋白对AP-1信号通路的调控作用.MTT和流式细胞术实验发现,R8-HBAP能抑制ATL细胞的恶性增殖并促进细胞凋亡.因此,靶向多肽R8-HBAP通过阻遏HBZ蛋白的功能从而抑制白血病细胞的恶性增殖,为R8-HBAP的开发利用及成人T细胞白血病的治疗提供一定的实验依据.
