Database Study on the Expression and Purification of Membrane Proteins

Whole-genome sequencing of Sphingobium baderi SC-1 and identification of a crucial 3-phenoxybenzoic acid-degrading gene

As an efficient degradation strain, Sphingobium baderi SC-1 can breakdown 3-phenoxybenzoic acid (3-PBA) with high proficiency. To investigate the internal factors that regulate this process, we conducted whole-genome sequencing and successfully identified the pivotal 3-PBA-degrading gene sca (1,230 bp). After sca was expressed in engineered bacteria, a remarkable degradation efficiency was observed, as 20 mg/L 3-PBA was almost completely decomposed within 24 h. The phenol was formed as one of the degradation products. Notably, in addition to their ability to degrade 3-PBA, the resting cells proficiently degraded 4'-HO-3-PBA and 3'-HO-4-PBA. In conclusion, we successfully identified and validated sca as the pivotal enzyme responsible for the efficient degradation of 3-PBA from Sphingomonas baderi, providing a crucial theoretical foundation for further explorations on the degradation potential of SC-1.

Enhanced recombinant protein capture, purity and yield from crude bacterial cell extracts by N-Lauroylsarcosine-assisted affinity chromatography

BACKGROUND

Recombinant proteins cover a wide range of biomedical, biotechnological, and industrial needs. Although there are diverse available protocols for their purification from cell extracts or from culture media, many proteins of interest such as those containing cationic domains are difficult to purify, a fact that results in low yields of the final functional product. Unfortunately, this issue prevents the further development and industrial or clinical application of these otherwise interesting products.

RESULTS

Aiming at improving the purification of such difficult proteins, a novel procedure has been developed based on supplementing crude cell extracts with non-denaturing concentrations of the anionic detergent N-Lauroylsarcosine. The incorporation of this simple step in the downstream pipeline results in a substantial improvement of the protein capture by affinity chromatography, an increase of protein purity and an enhancement of the overall process yield, being the detergent not detectable in the final product.

CONCLUSION

By taking this approach, which represents a smart repurposing of N-Lauroylsarcosine applied to protein downstream, the biological activity of the protein is not affected. Being technologically simple, the N-Lauroylsarcosine-assisted protein purification might represent a critical improvement in recombinant protein production with wide applicability, thus smothering the incorporation of promising proteins into the protein market.

Expression and purification of soluble recombinant β-lactamases using Escherichia coli as expression host and pET-28a as cloning vector

Background

Due to its high expression capability, recombination of Escherichia coli and pET vector has become the bioengineering preferred expression system. Because β-lactamases mediate bacterial antimicrobial resistance, these enzymes have a substantial clinical impact. Using the E. coli expression system, several kinds of β-lactamases have been produced. However, previous studies have been focused on characterizing target β-lactamases, and the effects of cultivation and induction conditions on the expression efficiency of target enzymes were not addressed.

Results

Using pET-28a as the cloning vector and E. coli BL21(DE3) as the expression host, this study originally elucidated the effects of IPTG concentration, culture temperature, induction time, and restriction sites on recombinant β-lactamase expression. Moreover, the effects of the target protein length and the 6 × His-tag fusion position on enzyme purification were also explored, and consequently, this study yielded several important findings. (i) Only the signal peptide–detached recombinant β-lactamase could exist in a soluble form. (ii) Low-temperature induction was beneficial for soluble β-lactamase expression. (iii) The closer to the rbs the selected restriction site was, the more difficult it was to express soluble β-lactamase. (iv) The short-chain recombinant protein and the protein with His-tag fused at its C-terminus showed high affinity to the Ni²⁺ column.

Conclusions

Based on our findings, researchers can easily design an effective program for the high production of soluble recombinant β-lactamases to facilitate other related studies.

Expression of the Heterotrimeric GP2/GP3/GP4 Spike of an Arterivirus in Mammalian Cells

Equine arteritis virus (EAV), an enveloped positive-strand RNA virus, is an important pathogen of horses and the prototype member of the Arteiviridae family. Unlike many other enveloped viruses, which possess homotrimeric spikes, the spike responsible for cellular tropism in Arteriviruses is a heterotrimer composed of 3 glycoproteins: GP2, GP3, and GP4. Together with the hydrophobic protein E they are the minor components of virus particles. We describe the expression of all 3 minor glycoproteins, each equipped with a different tag, from a multi-cassette system in mammalian BHK-21 cells. Coprecipitation studies suggest that a rather small faction of GP2, GP3, and GP4 form dimeric or trimeric complexes. GP2, GP3, and GP4 co-localize with each other and also, albeit weaker, with the E-protein. The co-localization of GP3-HA and GP2-myc was tested with markers for ER, ERGIC, and cis-Golgi. The co-localization of GP3-HA was the same regardless of whether it was expressed alone or as a complex, whereas the transport of GP2-myc to cis-Golgi was higher when this protein was expressed as a complex. The glycosylation pattern was also independent of whether the proteins were expressed alone or together. The recombinant spike might be a tool for basic research but might also be used as a subunit vaccine for horses.