A member of a specific binding pair (sbp) is identified by expressing
DNA encoding a genetically
diverse population of such sbp members in recombinant host cells in which the sbp members are displayed in functional form at the surface of a secreted recombinant genetic display
package (rgdp) containing
DNA encoding the sbp member or a polypeptide component thereof, by virtue of the sbp member or a polypeptide component thereof being expressed as a fusion with a
capsid component of the rgdp. The displayed sbps may be selected by affinity with a complementary sbp member, and the
DNA recovered from selected rgdps for expression of the selected sbp members.
Antibody sbp members may be thus obtained, with the different chains thereof expressed, one fused to the
capsid component and the other in
free form for association with the fusion partner polypeptide. A
phagemid may be used as an
expression vector, with said
capsid fusion helping to
package the
phagemid DNA. Using this method libraries of
DNA encoding respective chains of such multimeric sbp members may be combined, thereby obtaining a much greater
genetic diversity in the sbp members than could easily be obtained by conventional methods.