Cytoplasmic bacteriophage display system

DETAILED DESCRIPTION The present invention relates, in one aspect, to a display vector comprising DNA encoding a portion of a structural protein from a cytoplasmic bacteriophage, joined covalently to a protein or peptide of interest.
In preferred embodiments, the structural protein is selected from the group consisting of capsid, tail, tail-fiber and head-tail connector proteins.
Exemplified are display vectors wherein the structural protein is the T7 bacteriophage capsid protein.
More specifically, in the exemplified display vectors the C-terminal amino acid residue of the portion of the capsid protein is joined to the N-terminal residue of the protein or peptide of interest.
The portion of the T7 capsid protein exemplified comprises an N-terminal portion corresponding to form 10B of the T7 capsid protein.
In preferred embodiments in which high copy number display is desired, wild-type T7 capsid protein regulatory signals are employed (e.
g.
, promoter and translation initiation signals).
Other embodiments which are useful for producing larger fusion at a lower copy number on the assembled viral capsid lack wild-type capsid protein promoter and translation initiation signals.
The subject invention also relates to cells containing a display vector of the type described above.
Viral lysates containing assembled cytoplasmic bacteriophage particles bearing fusions to a cytoplasmic structural protein are also encompassed.
Compositions of the type described above are useful in connection with methods for producing a virus displaying a protein or peptide of interest.
In such methods, a virus- based display vector of the type described above is used to clone DNA fragments such that the display vector encodes a fusion protein comprising the portion of the structural protein fused to protein or peptide sequences encoded by the DNA fragments.
Cells are then infected with the virus-based display vector and viral lysates are screened to identify viral particles in which the protein or peptide of interest is expressed as a fusion protein joined to the structural gene from the cytoplasmic bacteriophage