Abstract
BackgroundAffinity chromatography is one of the most efficient protein purification strategies. This technique comprises a one-step procedure with a purification level in the order of several thousand-fold, adaptable for various proteins, differentiated in their size, shape, charge, and other properties. The aim of this work was to verify the possibility of applying affinity chromatography in bacteriophage purification, with the perspective of therapeutic purposes. T4 is a large, icosahedral phage that may serve as an efficient display platform for foreign peptides or proteins. Here we propose a new method of T4 phage purification by affinity chromatography after its modification with affinity tags (GST and Histag) by in vivo phage display. As any permanent introduction of extraneous DNA into a phage genome is strongly unfavourable for medical purposes, integration of foreign motifs with the phage genome was not applied. The phage was propagated in bacteria expressing fusions of the phage protein Hoc with affinity tags from bacterial plasmids, independently from the phage expression system.ResultsElution profiles of phages modified with the specific affinity motifs (compared to non-specific phages) document their binding to the affinity resins and effective elution with standard competitive agents. Non-specific binding was also observed, but was 102-105 times weaker than the specific one. GST-modified bacteriophages were also effectively released from glutathione Sepharose by proteolytic cleavage. The possibility of proteolytic release was designed at the stage of expression vector construction. Decrease in LPS content in phage preparations was dependent on the washing intensity; intensive washing resulted in preparations of 11-40 EU/ml.ConclusionsAffinity tags can be successfully incorporated into the T4 phage capsid by the in vivo phage display technique and they strongly elevate bacteriophage affinity to a specific resin. Affinity chromatography can be considered as a new phage purification method, appropriate for further investigations and development.
Highlights
Affinity chromatography is one of the most efficient protein purification strategies
Expression of the fusion proteins gpHoc with affinity tags (GST or His tag) was tested in an expression E. coli strain before the procedure of phage capsid modification by phage display
The expression vectors were used for simultaneous expression of fusion proteins and propagation of bacteriophage HAP1 in E. coli, i.e. phage display in vivo
Summary
Affinity chromatography is one of the most efficient protein purification strategies. Therapeutic use of bacteriophages requires large-scale preparations that may be obtained by various chromatography techniques [4,5,6]. In these assays in vivo, often require large amounts of highly purified phages. In these cases currently used procedures still do not provide satisfactory results and there is an important need to develop phage purification methods
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