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Phage display is a method for the study of protein-protein, protein-peptide, and protein-DNA interactions that uses bacteriophages to connect proteins with the genetic information that encodes them.[1] Phage Display was originally invented by George.P. Smith in 1985 and he demonstrated the display of petides on filamentous phage by fusing the peptide of interest on to gene3 of filamentous phage.[1] This technology was further developed and improved by various other people like John McCafferty for the display of proteins like antibodies for therapeutic protein engineering. The connection between genotype and phenotype enables large libraries of proteins to be screened and amplified in a process called in vitro selection, which is analogous to natural selection. The most common bacteriophages used in phage display are M13 and fd filamentous phage,[2][3] though T4[4], T7, and λ phage have also been used.



Like the two-hybrid system, phage display is used for the high-throughput screening of protein interactions. In the case of M13 filamentous phage display, the DNA encoding the protein or peptide of interest is ligated into the pIII or pVIII gene. Multiple cloning sites are sometimes used to ensure that the fragments are inserted in all three possible frames so that the cDNA fragment is translated in the proper frame. The phage gene and insert DNA hybrid is then transformed into E. coli bacterial cells such as TG1 or XL1-Blue E. coli. If a "phagemid" vector is used (a simplified display construct vector) phage particles will not be released from the E. coli cells until they are infected with helper phage, which enables packaging of the phage DNA and assembly of the mature virions with the relevant protein fragment as part of their outer coat on either the minor (pIII) or major (pVIII) coat protein. The incorporation of many different DNA fragments into the pIII or pVIII genes generates a library from which members of interest can be isolated.

By immobilising a relevant DNA or protein target(s) to the surface of a well, a phage that displays a protein that binds to one of those targets on its surface will remain while others are removed by washing. Those that remain can be eluted, used to produce more phage (by bacterial infection with helper phage) and so produce a phage mixture that is enriched with relevant (i.e. binding) phage. The repeated cycling of these steps is referred to as 'panning', in reference to the enrichment of a sample of gold by removing undesirable materials.

Phage eluted in the final step can be used to infect a suitable bacterial host, from which the phagemids can be collected and the relevant DNA sequence excised and sequenced to identify the relevant, interacting proteins or protein fragments.

Recent work published by Chasteen et al., shows that use of the helper phage can be eliminated by using a novel 'bacterial packaging cell line' technology.[5]

General protocol

  1. Target proteins or DNA sequences are immobilised to the wells of a microtiter plate.
  2. Many genetic sequences are expressed in a bacteriophage library in the form of fusions with the bacteriophage coat protein, so that they are displayed on the surface of the viral particle. The protein displayed corresponds to the genetic sequence within the phage.
  3. This phage-display library is added to the dish and after allowing the phage time to bind, the dish is washed.
  4. Phage-displaying proteins that interact with the target molecules remain attached to the dish, while all others are washed away.
  5. Attached phage may be eluted and used to create more phage by infection of suitable bacterial hosts. The new phage constitutes an enriched mixture, containing considerably less irrelevant (i.e. non-binding phage) than were present in the initial mixture.
  6. The DNA within the interacting phage contains the sequences of interacting proteins, and following further bacterial-based amplification, can be sequenced to identify the relevant, interacting proteins or protein fragments.


The applications of this technology include determination of interaction partners of a protein (which would be used as the immobilised phage "bait" with a DNA library consisting of all coding sequences of a cell, tissue or organism) so that new functions or mechanisms of function of that protein may be inferred[6]. The technique is also used to determine tumour antigens (for use in diagnosis and therapeutic targeting)[7] and in searching for protein-DNA interactions[8] using specially-constructed DNA libraries with randomised segments.

Phage display is also a widely used method for in vitro protein evolution (also called protein engineering). As such, phage display is a useful tool in drug discovery. It is used for finding new ligands (enzyme inhibitors, receptor agonists and antagonists) to target proteins.[9][10][11].

Invention of antibody phage display by John McCafferty in 1990 revolutionised the drug discovery by allowing the display of antibody fragments on phage. [12] Antibody libraries displaying millions of different antibodies on phage are frequently used in the pharmaceutical industry for isolation of highly specific therapeutic antibody leads, for development into primarily anti-cancer or anti-inflammatory antibody drugs. One of the most successful was HUMIRA (adalimumab), discovered by Cambridge Antibody Technology as D2E7 and developed and marketed by Abbott Laboratories. HUMIRA, an antibody to TNF alpha, was the world's first fully human antibody[13], which achieved annual sales exceeding $1bn [14] therefore achieving blockbuster status[15].

Competing methods for in vitro protein evolution are yeast display, bacterial display, ribosome display, and mRNA display.

See also


  1. ^ a b Smith GP (1985). "Filamentous fusion phage: novel expression vectors that display cloned antigens on the virion surface". Science 228 (4705): 1315–1317. doi:10.1126/science.4001944. PMID 4001944. 
  2. ^ Smith GP, Petrenko VA (1997). "Phage display". Chem. Rev. 97 (2): 391–410. doi:10.1021/cr960065d. 
  3. ^ Kehoe JW, Kay BK (2005). "Filamentous phage display in the new millennium". Chem. Rev. 105 (11): 4056–4072. doi:10.1021/cr000261r. 
  4. ^ Malys N, Chang DY, Baumann RG, Xie D, Black LW (2002). "A bipartite bacteriophage T4 SOC and HOC randomized peptide display library: detection and analysis of phage T4 terminase (gp17) and late sigma factor (gp55) interaction". J Mol Biol 319 (2): 289-304. doi:10.1016/S0022-2836(02)00298-X. 
  5. ^ Chasteen L, Ayriss J, Pavlik P, Bradbury AR. Eliminating helper phage from phage display. Nucleic Acids Res. 2006;34(21):e145. Epub 2006 Nov 6.PMID: 17088290
  6. ^ Explanation of "Protein interaction mapping" from The Wellcome Trust
  7. ^ Hufton SE, Moerkerk PT, Meulemans EV, de Bruïne A, Arends JW, Hoogenboom HR (1999). "Phage display of cDNA repertoires: the pVI display system and its applications for the selection of immunogenic ligands". J. Immunol. Methods 231 (1-2): 39–51. doi:10.1016/S0022-1759(99)00139-8. PMID 10648926. 
  8. ^ Gommans WM, Haisma HJ, Rots MG (2005). "Engineering zinc finger protein transcription factors: the therapeutic relevance of switching endogenous gene expression on or off at command". J. Mol. Biol. 354 (3): 507–19. doi:10.1016/j.jmb.2005.06.082. PMID 16253273. 
  9. ^ Lunder M, Bratkovic T, Doljak B, Kreft S, Urleb U, Strukelj B, Plazar N. (2005). "Comparison of bacterial and phage display peptide libraries in search of target-binding motif". Appl. Biochem. Biotechnol. 127 (2): 125–31. doi:10.1385/ABAB:127:2:125. 
  10. ^ Bratkovic T, Lunder M, Popovic T, Kreft S, Turk B, Strukelj B, Urleb U. (2005). "Affinity selection to papain yields potent peptide inhibitors of cathepsins L, B, H, and K". Biochem. Biophys. Res. Commun. 332 (3): 897–903. doi:10.1016/j.bbrc.2005.05.028. 
  11. ^ Lunder M, Bratkovic T, Kreft S, Strukelj B (2005). "Peptide inhibitor of pancreatic lipase selected by phage display using different elution strategies". J. Lipid Res. 2005 46 (7): 1512–6. doi:10.1194/jlr.M500048-JLR200. PMID 15863836. 
  12. ^ McCafferty J, Griffiths A.D, Winter G, Chiswell D.J. "Phage antibodies: filamentous phage displaying antibody variable domains". Nature 1990 volume=348 (63017): 552-554. 
  13. ^
  14. ^
  15. ^

See also

McCafferty, J., Griffiths, A.D., Winter, G. and Chiswell, D.J. 1990. Phage antibodies: filamentous phage displaying antibody variable domains. Nature 348: 552−554.



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