Curcin, a ribosome-inactivating protein with a molecular weight of about 28.2 kD, which strongly inhibits the protein synthesis in rabbit reticulocyte lysate system with an IC50 value of about (0.19 +/- 0.01) nmol/L, ...Curcin, a ribosome-inactivating protein with a molecular weight of about 28.2 kD, which strongly inhibits the protein synthesis in rabbit reticulocyte lysate system with an IC50 value of about (0.19 +/- 0.01) nmol/L, was purified from the seeds of Jatropha curcas L. The protein has the activity of rRNA N-glycosidase. Degenerate primers were designed based on the N-terminal partial sequence from purified curcin. The full-length curcin cDNA by RT-PCR and 5'-RACE was cloned. The deduced amino acids sequence indicates that a preprotein with 20 amino acid residues is first translated and then processed to a mature protein with 251 amino acids. The deduced amino acids sequence shares homology of 33% and 57% to those of type I ribosome-inactivating proteins (RIPs) and A chain of type II RIPs, respectively. The sequence encoding mature curcin was integrated into the pQE-30 vector for expression in Escherichia coli strain M15 (pREP4). The purified recombinant curcin was able to inhibit protein synthesis in rabbit reticulocyte lysate system.展开更多
Many plants contain ribosome inactivating proteins (RIPs) with N-glycosidase activity, which depurinate large ribosomal RNA and arrest protein synthesis. RIPs so far tested inhibit replication of mRNA as well as DNA v...Many plants contain ribosome inactivating proteins (RIPs) with N-glycosidase activity, which depurinate large ribosomal RNA and arrest protein synthesis. RIPs so far tested inhibit replication of mRNA as well as DNA viruses and these proteins, isolated from plants, are found to be effective against a broad range of viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV) and herpes simplex virus (HSV). Most of the research work related to RIPs has been focused on antiviral activity against HIV; however, the exact mechanism of antiviral activity is still not clear. The mechanism of antiviral activity was thought to follow inactivation of the host cell ribosome, leading to inhibition of viral protein translation and host cell death. Enzymatic activity of RIPs is not limited to depurination of the large rRNA, in addition they can depurinate viral DNA as well as RNA. Recently, Phase I/II clinical trials have demonstrated the potential use of RIPs for treating patients with HIV disease. The aim of this review is to focus on various RIPs from plants associated with anti-HIV activity.展开更多
In this study,a series of 5′-phosphorylated siRNAs with D-/L-isonucleotide(isoNA)or locked nucleic acid(LNA)incorporated at the 5′-terminus were synthesized.It was found that after incorporating either isoNA or LNA ...In this study,a series of 5′-phosphorylated siRNAs with D-/L-isonucleotide(isoNA)or locked nucleic acid(LNA)incorporated at the 5′-terminus were synthesized.It was found that after incorporating either isoNA or LNA at the 5′-terminus of the antisense strand or sense strand,the silencing activity of modified strands has been inhibited,which cannot be recovered by phosphorylation at the 5′-terminus;however,the silencing activity of unmodified strand to its own target was increased.This work indicates that the isoNA and LNA modification at 5′-terminus can interfere with the strand selection during the RISC assembling process,and the disturbance of the 5′-phosporylation should not be the only viable mechanism.展开更多
文摘Curcin, a ribosome-inactivating protein with a molecular weight of about 28.2 kD, which strongly inhibits the protein synthesis in rabbit reticulocyte lysate system with an IC50 value of about (0.19 +/- 0.01) nmol/L, was purified from the seeds of Jatropha curcas L. The protein has the activity of rRNA N-glycosidase. Degenerate primers were designed based on the N-terminal partial sequence from purified curcin. The full-length curcin cDNA by RT-PCR and 5'-RACE was cloned. The deduced amino acids sequence indicates that a preprotein with 20 amino acid residues is first translated and then processed to a mature protein with 251 amino acids. The deduced amino acids sequence shares homology of 33% and 57% to those of type I ribosome-inactivating proteins (RIPs) and A chain of type II RIPs, respectively. The sequence encoding mature curcin was integrated into the pQE-30 vector for expression in Escherichia coli strain M15 (pREP4). The purified recombinant curcin was able to inhibit protein synthesis in rabbit reticulocyte lysate system.
基金Indo-Swiss Joint research Program (ISJRP)#17/2011
文摘Many plants contain ribosome inactivating proteins (RIPs) with N-glycosidase activity, which depurinate large ribosomal RNA and arrest protein synthesis. RIPs so far tested inhibit replication of mRNA as well as DNA viruses and these proteins, isolated from plants, are found to be effective against a broad range of viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV) and herpes simplex virus (HSV). Most of the research work related to RIPs has been focused on antiviral activity against HIV; however, the exact mechanism of antiviral activity is still not clear. The mechanism of antiviral activity was thought to follow inactivation of the host cell ribosome, leading to inhibition of viral protein translation and host cell death. Enzymatic activity of RIPs is not limited to depurination of the large rRNA, in addition they can depurinate viral DNA as well as RNA. Recently, Phase I/II clinical trials have demonstrated the potential use of RIPs for treating patients with HIV disease. The aim of this review is to focus on various RIPs from plants associated with anti-HIV activity.
基金supported by the National Natural Sciences Foundation of China(20932001)the Program of the Ministry of Science and Technology of China(2009ZX09503,2012AA022501,2012CB720604)
文摘In this study,a series of 5′-phosphorylated siRNAs with D-/L-isonucleotide(isoNA)or locked nucleic acid(LNA)incorporated at the 5′-terminus were synthesized.It was found that after incorporating either isoNA or LNA at the 5′-terminus of the antisense strand or sense strand,the silencing activity of modified strands has been inhibited,which cannot be recovered by phosphorylation at the 5′-terminus;however,the silencing activity of unmodified strand to its own target was increased.This work indicates that the isoNA and LNA modification at 5′-terminus can interfere with the strand selection during the RISC assembling process,and the disturbance of the 5′-phosporylation should not be the only viable mechanism.
