A hemolysin secretion pathway-based novel secretory expression platform for efficient manufacturing of tag peptides and anti-microbial peptides in Escherichia coli

Background Although Escherichia coli has been widely used for the expression of exogenous proteins, the secretory expression in this system is still a big obstacle. As one of the most important secretion pathways, hemolysin A (HlyA) system of E. coli can transport substrates directly from the cytoplasm to extracellular medium without the formation of any periplasmic intermediate, making it an ideal candidate for the development of the secretory production platform for exogenous proteins. Results In this work, we developed a novel production platform, THHly, based on the HlyA secretion system, and explored its applications in the efficient preparation and quick detection of tag peptides and anti-microbial peptides. In this novel platform the signal sequence of HlyA is fused to the C-terminal of target peptide, with Tobacco Etch Virus (TEV) protease cleavage site and 6*His tag between them. Five tag peptides displayed good secretory properties in E. coli BL21 (DE3), among which T7 tag and S tag were obtained by two rounds of purification steps and TEV cleavage, and maintained their intrinsic immunogenicity. Furthermore, Cecropin A and Melittin, two different types of widely explored anti-microbial peptides, were produced likewise and verified to possess anti-microbial/anti-tumor bioactivities. No significant bacterial growth inhibition was observed during the fusion protein expression, indicating that the fusion form not only mediated the secretion but also decreased the toxicity of anti-microbial peptides (AMPs) to the host bacteria. To the best of our knowledge, this is the first report to achieve the secretory expression of these two AMPs in E. coli with considerable potential for manufacturing and industrialization purposes. Conclusions The results demonstrate that the HlyA based novel production platform of E. coli allowed the efficient secretory production and purification of peptides, thus suggesting a promising strategy for the industrialized production of peptide pharmaceuticals or reagents. Graphical Abstract

HALO-RPD: In Searching for RNA-Binding Protein Targets in Plants

Study of RNA-protein interactions and identification of RNA targets are among the key aspects of understanding the RNA biology. Currently, various methods are available to investigate these interactions, in particular, RNA pulldown assay. In the present paper, a method based on the HaloTag technology is presented that is called Halo-RPD (HaloTag RNA PullDown). The proposed protocol uses plants with stable fusion protein expression and the MagneBeads magnetic beads to capture RNA-protein complexes directly from the cytoplasmic lysate of transgenic A. thaliana plants. The key stages described in the paper are as follows: 1) preparation of the magnetic beads 2) tissue homogenization and collection of control samples 3) precipitation and wash of RNA-protein complexes; 4) evaluation of protein binding efficacy; 5) RNA isolation; 6) analysis of the obtained RNA. Recommendations for better NGS assay designs are provided.

Recombinant fusion protein expression of Indonesian isolate Newcastle disease virus in Escherichia coli BL21(DE3)

Wulanjati MP, Witasari LD, Wijayanti N, Haryanto A. 2021. Recombinant fusion protein expression of Indonesian isolate Newcastle disease virus in Escherichia coli BL21(DE3). Biodiversitas 22: 3249-3255. Newcastle disease is a major problem in poultry industry due to high mortality of susceptible chicken. New vaccine agents are important to be developed to eliminate the disease threat. This study aimed to examine the expression of fusion (F) protein of Newcastle Disease Virus (NDV) from Indonesian isolates in E. coli BL21(DE3) by IPTG induction. The sample was a part of F gene of NDV from Galur, Kulon Progo, Yogyakarta, Indonesia (0663/04/2013) with a molecular size of 600 bp that was synthesized and inserted into pBT7-N-His expression vector. The recombinant F protein with molecular weight of 25.6 kDa was successfully expressed in E. coli BL21(DE3), purified using Ni-NTA magnetic silica beads, and confirmed by western blotting. Optimization of expression showed that recombinant F protein was optimally expressed by induction of 1.0 mM IPTG when the cells reached OD600 = 0.6. The induction duration was 8 h. B-cell epitopes prediction showed that F protein possessed four epitopes that possibly recognized by B-cell. Since recombinant F protein was considered to possess immunogenicity, its potency as a candidate of NDV vaccine agent should be investigated in the future.