FIG. 2.
Modifications of the HI loop of the fiber knob. PCR-based mutagenesis was employed to delete a portion of the fiber gene encoding the hypervariable region of the HI loop. A unique EcoRV restriction site was incorporated in place of the deletion to allow the cloning of segments of DNA coding for heterologous protein sequences. In the fiber-FLAG protein, deleted amino acids of the HI loop were restored, and FLAG octapeptide was incorporated between threonine-546 and proline-547. The site of deletion is indicated by a filled triangle.