Cloning of ligand-binding domains of bacterial receptors by phage display

We present an application of the phage display technique which makes it possible, through affinity selection, to clone the part of a prokaryotic receptor gene that encodes the ligand-binding domain. A phage display library was constructed by insertion of randomly fragmented chromosomal DNA from Staphylococcus aureus strain 8325-4 into the phagemid vector pHEN1. Domains of the genes encoding staphylococcal protein A and fibronectin binding proteins were isolated from the library by affinity panning of the phage against the immobilized ligands. Approximately 1%-10% of the eluted phage encoded polypeptides that specifically bound the respective ligand. Nucleotide sequences of the isolated clones were in agreement with earlier known sequences of domains encoding the IgG and fibronectin-binding proteins. In addition, a second, so far unknown, nucleotide sequence encoding an IgG-binding polypeptide was identified.