THE MALTOSE-BINDING PROTEIN AS A SCAFFOLD FOR MONOVALENT DISPLAY OF PEPTIDES DERIVED FROM PHAGE LIBRARIES

Random peptide libraries are displayed on filamentous bacteriophage as fusions to either the minor coat protein, pIII, or the major coat pro tein, pVIII. We have devised a means of isolating the peptide displaye d on a phage clone by transferring it to the N-terminus of the maltose -binding protein (MBP) of Escherichia coli encoded by malE. Transfer o f a peptide sequence to monomeric MBP eliminates phage-encoded amino a cids downstream of the insert peptide as well as avidity effects cause d by multivalent display on phage. Peptide:MBP fusions are also easily affinity purified on amylose columns. The pMal-p2 vector was engineer ed to accept phage DNA encoding pIII- and pVIII-displayed peptides fus ed to their respective leader sequences. Both types of leader sequence were shown to target the peptide:MBP fusions to the periplasm off. co li. A streamlined procedure for transferring peptides to MBP was appli ed to clones that had been isolated from a panel of pVIII-displayed pe ptide libraries by screening with an HIV-1-specific monoclonal antibod y (Ab). By enzyme-linked immunosorbent assay, the Ab bound each of the peptide:MBP fusions and required the presence of a disulfide bridge w ithin each peptide. Some of the peptide:MBP fusions were also analyzed using surface plasmon resonance. Thus, our study shows the value of m alE fusion vectors in characterizing phage-displayed peptides. (C) 199 8 Academic Press.