Phage display technology is a powerful molecular tool that has played a significant role in biotechnology and medical research since the late 1980s. The characteristic of phages is their ability to infect bacteria and other microorganisms, utilizing their cellular machinery for self-replication. The phage display system leverages this property by inserting exogenous proteins or peptides into the phage genome, enabling the phage to express and display these foreign proteins or peptides. The applications of phage display technology are extensive, ranging from drug development to vaccine design and the creation of diagnostic tools. The origin of phage display technology can be traced back to 1985, when George P. Smith first demonstrated the surface display of exogenous peptides on phages. This technology rapidly gained widespread application in the fields of molecular biology and protein engineering, becoming a powerful tool for studying protein-protein interactions, epitope mapping, and antibody engineering.

In phage display technology, different types of phage systems each possess distinct characteristics, primarily including the M13 phage, T7, and T4 phage systems. These systems vary in terms of protein display diversity, stability, and efficiency, catering to different research and application requirements. This article will focus on exploring the similarities and differences among the M13, T7, and T4 phage systems:

M13 Phage Display System: 

The M13 phage primarily utilizes pIII and pVIII capsid proteins to construct its display system. pIII is distributed at one end of the phage particle and can insert larger molecular weight foreign peptides/proteins into the flexible N-terminal linker region, making it suitable for displaying larger molecular weight proteins. pVIII is mainly distributed on both sides of the phage particle, with a smaller molecular weight and higher copy number, thus only applicable for displaying short foreign peptides. Currently, it is primarily used for screening low-affinity ligands.

T4 phage display system:

 T4 phages are frequently employed to study complex proteins that cannot be secreted by E. coli, as their viral particle assembly occurs within host cells, eliminating the need for secretion pathways to display various polypeptides or proteins. Additionally, the capsid proteins of T4 phages possess two binding sites—the SOC site and the HOC site—endowing the phage with the capability to fuse two distinct exogenous polypeptides/proteins and simultaneously display them on its surface, with a high copy number of displayed proteins.

T7 phage display system:

The capsid protein 10B of T7 phage is commonly used to construct phage display systems. Compared to M13, it does not require secretion and can directly induce host bacterial lysis. Therefore, it is suitable for displaying peptides/proteins that are inhibited by the secretion process and cannot be expressed in the M13 system. Additionally, the production of T7 phage is highly efficient, saving significant time and facilitating research.

The following table compares and elaborates on the characteristics, diversity, stability, and assembly efficiency of three different phage display systems:

Table 1 Comparison of several different phage display systems:

The M13 and T7 phage systems each exhibit distinct advantages and limitations in terms of diversity, stability, and efficiency. The selection of a specific system depends on the experimental objectives and requirements. The M13 system is more suitable for the display and long-term screening of small-molecule peptides, whereas the T7 system demonstrates strengths in the rapid expression and high-throughput screening of large-molecule proteins. Proper selection of an appropriate phage system is critical to ensuring experimental success and obtaining reliable results. The T4 phage system offers a unique option in protein display technology, particularly for handling large-molecule proteins or conducting high-throughput screening.