Expression, purification, and characterization of transmembrane protein homogentisate solanesyltransferase

Homogentisate solanesyltransferase (HST) is a crucial enzyme in the plastoquinone biosynthetic pathway and has recently emerged as a promising target for herbicides. In this study, we successfully expressed and purified a stable and highly pure form of seven times transmembrane protein Chlamydomonas reinhardtii HST (CrHST). The final yield of CrHST protein obtained was 12.2 mg per liter of M9 medium. We evaluated the inhibitory effect on CrHST using Des-Morpholinocarbony Cyclopyrimorate (DMC) and found its IC50 value to be 3.63 ± 0.53 μM, indicating significant inhibitory potential. Additionally, we investigated the substrate affinity of CrHST with two substrates, determining the Km values as 22.76 ± 1.70 μM for FPP and 48.54 ± 3.89 μM for HGA. Through sequence alignment analyses and three-dimensional structure predictions, we identified conserved amino acid residues forming the active cavity in the enzyme. The results from molecular docking and binding energy calculations indicate that DMC has a greater binding affinity with HST compared to HGA. These findings represent substantial progress in understanding CrHST's properties and potential for herbicide development. KEY POINTS: • First high-yield transmembrane CrHST protein via E. coli system • Preliminarily identified active cavity composition via activity testing • Determined substrate and inhibitor modes via molecular docking.

Immunization with recombinant ORF2 p551 protein protects common marmosets (Callithrix jacchus) against homologous and heterologous hepatitis E virus challenge

BACKGROUND

Hepatitis E virus (HEV) is a major causative agent of acute hepatitis worldwide, prompting continuous HEV vaccine efforts. Vaccine development is hampered by the lack of convenient animal models susceptible to infection with different HEV genotypes. We produced recombinant open reading frame 2 protein (pORF2; p551) of HEV genotype (GT) 3 and assessed its immunogenicity and protectivity against HEV challenge in common marmosets (Callithrix jacchus, CM).

METHODS

p551 with consensus sequence corresponding to amino acid residues 110-660 of HEV GT3 pORF2 was expressed in E. coli and purified by affinity chromatography. CMs were immunized intramuscularly with 20 μg of p551 VLPs with alum adjuvant (n = 4) or adjuvant alone (n = 2) at weeks 0, 3, 7 and 19. At week 27, p551-immunized and control animals were challenged with HEV GT1 or GT3 and thereafter longitudinally screened for markers of liver function, anti-HEV IgG and HEV RNA in feces and sera.

RESULTS

Purified p551 formed VLPs with particle size of 27.71 ± 2.42 nm. Two immunizations with p551 induced anti-HEV IgG mean titer of 1:1810. Immunized CMs challenged with homologous and heterologous HEV genotype did not develop HEV infection during the follow-up. Control CMs infected with both HEV GT1 and GT3 demonstrated signs of HEV infection with virus shedding and elevation of the levels of liver enzymes. High levels of anti-HEV IgG persisted in vaccinated CMs and control CMs that resolved HEV infection, for up to two years post challenge.

CONCLUSIONS

CMs are shown to be a convenient laboratory animal model susceptible to infection with HEV GT1 and GT3. Immunization with HEV GT3 ORF2/p551 triggers potent anti-HEV antibody response protecting CMs from homologous and heterologous HEV challenge. This advances p551 in VLPs as a prototype vaccine against HEV.

Bacterial expression and characterization of an anti-CD22 single-chain antibody fragment

Single-chain variable fragment (scFv) antibodies are fusion proteins of the variable regions of the heavy and light chains of immunoglobulins connected with a short linker peptide. They possess unique and superior features compared to whole antibodies for immunotherapy of various carcinomas, including hematologic B-cell malignancies. In the presented study we obtained efficient production of the recombinant anti-CD22 scFv in Escherichia coli expression system. The active recombinant protein was successfully recovered from inclusion bodies. Assays were performed to assess the in vitro targeting properties and specificity of the obtained anti-CD22 scFv antibody in the CD22 positive and negative lymphoma cell lines.

Novel Expression Vectors Based on the pIGDM1 Plasmid

Escherichia coli is one of the most widely used hosts for the production of heterologous proteins. Within this host, the choice of cloning vector constitutes a key factor for a satisfactory amplified expression of a target gene. We aimed to develop novel, unpatented expression vectors that enable the stable maintenance and efficient overproduction of proteins in E. coli. A series of expression vectors based on the ColE1-like pIGDM1 plasmid were constructed. The vectors named pIGDMCT7RS, pIGDM4RS and pIGDMKAN carry various antibiotic resistance genes: chloramphenicol, ampicillin or kanamycin, respectively. Two derivatives contain the inducible T7 promoter while the third one bears the constitutive pms promoter from a clinical strain of Klebsiella pneumoniae. The pIGDM1-derivatives are compatible with other ColE1-like plasmids commonly used in molecular cloning. The pIGDMCT7RS and pIGDM4RS vectors contain genes encoding AGA and AGG tRNAs, which supplement the shortage of these tRNAs, increasing the efficiency of synthesis of heterologous proteins. In conclusion, pIGDMCT7RS, pIGDM4RS and pIGDMKAN vectors, with significantly improved features, including compatibility with vast majority of other plasmids, were designed and constructed. They enable a high-level expression of a desired recombinant gene and therefore constitute a potential, valuable tool for pharmaceutical companies and research laboratories for their own research or for the production of recombinant biopharmaceuticals.

Surface plasmon resonance (SPR) based binding studies of refolded single chain antibody fragments

Recent advances in Recombinant antibody technology / Antibody Engineering has given impetus to the genetic manipulation of antibody fragments that has paved the way for better understanding of the structure and functions of immunoglobulins and also has escalated their use in immunotherapy. Bacterial expression system such as Escherichia coli has complemented this technique through the expression of recombinant antibodies. Present communication has attempted to optimize the expression and refolding protocol of single chain fragment variable (ScFv) and single chain antigen binding fragment (ScFab) using E.coli expression system. Efficiency of refolding protocol was validated by structural analysis by CD, native folding by fluorescence and functional analysis by its binding with full length HIV-1 gp120 via SPR. Results show the predominant β–sheet (CD) as secondary structural content and native folding via red shift (tryptophan fluorescence). The single chain fragments have shown good binding with HIV-1 gp120 thus validating the expression and refolding strategy and also reinstating E.coli as model expression system for recombinant antibody engineering. SPR based binding analysis coupled with E.coli based expression and purification will have implication for HIV therapeutics and will set a benchmark for future studies of similar kind.

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A scFv having V_H and V_L chains joined through a peptide linker and expressed in E.coli.

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Functional analysis by SPR show good bindng with full length HIV-1 gp120.

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Protein engineering facilitated improvised scFv with enhanced affinity and specificity.

Improved method for assembly of hemeprotein neuronal NO-synthase heterodimers

The assembly of mutated and wild type monomers into functional heterodimeric hemeproteins has provided important mechanistic insights. As in the case of NO synthase (NOS), the existing methods to make such heterodimeric NOSs are inefficient and labor intensive with typical yields of about 5%. We have found that expression of neuronal NOS heterodimers in insect cells, where we take advantage of an exogenous heme-triggered chaperone-assisted assembly process, provides an approximately 43% yield in heterodimeric NOS. In contrast, in Escherichia coli little heterodimerization occurred. Thus, insect cells are preferred and may represent a valuable method for assembly of other dimeric hemeproteins.

Enhanced expression and purification of inositol 1,4,5-trisphosphate 3-kinase A through use of the pCold1-GST vector and a C-terminal hexahistidine tag in Escherichia coli

Inositol 1,4,5-trisphosphate 3-kinase A (IP3K-A, alternative name: ITPKA) is a neuron-specific enzyme that converts 1,4,5-trisphosphate (IP3) into inositol 1,3,4,5-tetrakisphosphate (IP4) through its kinase domain. In addition, transient overexpression of IP3K-A induces morphological changes in dendritic spines of excitatory synapses in a kinase-independent manner, apparently by modulating the organization of the neuronal cytoskeleton. Although the procurement of a purified recombinant IP3K-A protein would be indispensable for the biochemical elucidation of its physiological roles, production of recombinant IP3K-A has proven technically challenging in conventional Escherichia coli expression systems. These difficulties stem from low enzyme solubility, as well as poor protein quality caused by the tendency of IP3K-A to split into partial fragments. In present study, we newly introduced cold-shock expression vector (pCold1) together with a C-terminal hexahistidine tag (C-HIS) to enhance the expression levels of recombinant IP3K-A in E. coli. Importantly, when compared with other commonly-employed bacterial expression systems, the pCold1 system improved the yield and the purity of full-length IP3K-A due to the exclusion of truncated enzyme forms, and also enhanced the solubility of the enzyme. Furthermore, the functional integrity of purified IP3K-A was confirmed in both kinase activity assay and microtubule binding assay. Recombinant IP3K-A acquired via this modified protocol will be expected to facilitate the exploration of the enzyme's biochemical profile, both structurally and functionally.