Cloning of transcription factor PcFBA-1 in Pogostemon cabin and its interaction with FPPS promoter / 中国中药杂志

Farnesyl diphosphate synthase(FPPS) is a key enzyme at the branch point of the sesquiterpene biosynthetic pathway, but there are no reports on the transcriptional regulation of FPPS promoter in Pogostemon cabin. In the early stage of this study, we obtained the binding protein PcFBA-1 of FPPS gene promoter in P. cabin. In order to explore the possible mechanism of PcFBA-1 involved in the regulation of patchouli alcohol biosynthesis, this study performed PCR-based cloning and sequencing analysis of PcFBA-1, analyzed the expression patterns of PcFBA-1 in different tissues by fluorescence quantitative PCR and its subcellular localization using the protoplast transformation system, detected the binding of PcFBA-1 protein to the FPPS promoter in vitro with the yeast one-hybrid system, and verified its transcriptional regulatory function by dual-luciferase reporter gene assay. The findings demonstrated that the cloned PcFBA-1 had an open reading frame(ORF) of 1 131 bp, encoding a protein of 376 amino acids, containing two conserved domains named F-box-like superfamily and FBA-1 superfamily, and belonging to the F-box family. Moreover, neither signal peptide nor transmembrane domain was contained, implying that it was an unstable hydrophilic protein. In addition, as revealed by fluorescence quantitative PCR results, PcFBA-1 had the highest expression in leaves, and there was no significant difference in expression in roots or stems. PcFBA-1 protein was proved mainly located in the cytoplasm. Furthermore, yeast one-hybrid screening and dual-luciferase reporter gene assay showed that PcFBA-1 was able to bind to FPPS promoter both in vitro and in vivo to enhance the activity of FPPS promoter. In summary, this study identifies a new transcription factor PcFBA-1 in P. cabin, which directly binds to the FPPS gene promoter to enhance the promoter activity. This had laid a foundation for the biosynthesis of patchouli alcohol and other active ingre-dients and provided a basis for metabolic engineering and genetic improvement of P. cabin.

Mimotopes selected by biopanning with high-titer HIV-neutralizing antibodies in plasma from Chinese slow progressors

OBJECTIVE: One approach to identifying HIV-1 vaccine candidates is to dissect the natural antiviral immune response in treatment-naïve individuals infected for over ten years, considered slow progressor patients (SPs). It is suspected that SP plasma has strongly neutralizing antibodies (NAb) targeting specific HIV viral epitopes. METHODS: NAbs levels of 11 HIV-1-infected SPs were detected by PBMC-based neutralization assays. To investigate SP NAb epitope, this study used a biopanning approach to obtain mimotopes of HIV-1 that were recognized by SP plasma NAbs. IgG was purified from hightiter NAb SP plasma, and used as the ligand for three rounds of biopanning to select HIV-specific mimotopes from a phage-displayed random peptide library. Double-antibody sandwich ELISA, competitive inhibition assays, and peptide sequence analysis were used to evaluate the characteristics of phage-borne mimotopes. RESULTS: SPs had significantly more plasma neutralizing activity than typical progressors (TPs) (p = 0.04). P2 and P9 plasma, which have highest-titer HIV-NAb, were selected as ligands for biopanning. After three rounds of biopanning, 48 phage clones were obtained, of which 22 clones were consistent with requirement, binding with HIV-1 positive plasma and unbinding with HIV-1 negative plasma. Compared with linear HIV-1 protein sequence and HIV-1 protein structure files, only 12 clones were possible linear mimotopes of NAbs. In addition, the C40 clone located in gp41 CHR was found to be a neutralizing epitope, which could inhibit pooled HIV-1 positive plasma reaction. CONCLUSION: Biopanning of serum IgG can yield mimotopes of HIV-1-related antigen epitopes. This methodology provides a basis for exploration into HIV-1-related antigen-antibody interactions and furthers NAb immunotherapy and vaccine design.

Application of Element and Metabolism Balancing in the Production Phase of Human-like Collagen / 中国生物工程杂志

On the base of element and metabolism balancing,the mathematic model of the human-like collagen expression phase with recombinant Escherichia coli BL21 was developed and the unknown parameters in the model were estimated with the method of nonlinear optimization.The model was in agreement with the growth kinetics and the metabolic kinetics,and the key calculated parameters of ?h,?p and mx were 1.173 mol?C-mol-1,293.814 mol?C-mol-1 and 17.878 mol?C-mol-1?h-1 respectively.This model could preferably predict the macroscopic reaction rates,and in the synthesis phase of human-like collagen,the specific growth rate should be controlled at 0.04 h-1 with controlling glucose feeding rate to gain the highest specific production rate of human-like collagen.

Kinetics of Fed-batch Cultivation on Recombinant Escherichia coli Containing Human-like-Collagen cDNA / 中国生物工程杂志

The kinetics of batch and fed-batch cultures of recombinant Escherichia coli to produce humanlike collagen were investigated. Through examining the density of substrate and the amount of mushrooms and the density of products during the process of fermenting, a set of kinetic models are set up. The influence of cell without plasmid was considered. The results show that the kinetic model may well simulate the fermenting process.