Phage Display

Bacteriophage display, or phage display, can be defined as the process by which a protein or peptide that is foreign to the phage is expressed as an exterior fusion on the surface of the phage coat (called a capsid). This normally occurs as a genetic fusion to a coat protein gene of the phage which is then expressed as a physical fusion once the genes have been transcribed. This revolutionary technique is one of the largest innovations involving phage since their discovery in the early 1900's.

 

Figure 1: Overview of phage display

Smith (1985) was the first to successfully demonstrate a phage capsid fusion by inserting an external gene into the phage genome of fd phage for the efficient display of EcoRI endonuclease gene product on the fd minor coat protein pIII. Based on this initial work, lytic phage, including phage T4 and T7, and temperate phage λ (which is the phage that is used exclusively for this project) would eventually be successfully exploited as fusion vectors as well. The phage used in our lab, phage λ, contains an outer protein shell, or capsid, composed mainly of gene product E (gpE) in approximately 415 copies and gene product D which is present in 405-420 trimer-clustered molecules. The phage display with gpD can be seen on either the N- or C- terminus of gpD. We have previously developed a genetically tunable platform for phage display to have control over the numebr of fusions that we have per phage. This platform is now serving as a mechanism to fuse peptides onto the surface of our phage delivery vehicles to enhance their targeting and uptake.

 

Figure 2: Phage Lambda N- and C- terminal fusions

The newest phage construct, which we have made here in the lab, exhibits a fusion of a TAT (transactivator of transcription) peptide isolated from human immunodeficiency virus (HIV) that we believe will help with the cell penetration of our phage sample. We have named this phage: Phage Lambda Khilnani after one of our generous donors, and it will serve as one of the four main constructs that we will use in the HIV project. The phage is showing nice plaques grown on E. coli (which can be seen in Figure 3 below).

Thank you for all of your continued support.

Until next time,

The Slavcev Lab

 

Figure 3: Phage Lambda Khilnani