Conformation of Receptor Adopted upon Interaction with Virus Revealed by Site-Specific Fluorescence Quenchers and FRET-Analysis

Human rhinovirus serotype 2 (HRV2) specifically binds to very-low density lipoprotein receptor (VLDLR). Among the 8 extracellular repeats of VLDLR, the third module (V3) has the highest affinity for the virus and 12 copies of the genetically engineered concatamer V33333-His6 were found to bind per virus particle. In the present study, ring formation of V33333-His6 about each of the 12 five-fold symmetry axes on HRV2 was demonstrated by fluorescence resonance energy transfer (FRET) between donor and acceptor on N- and C-terminus, respectively. In particular, the N-terminus of V33333-His6 was labeled with fluorescein, and the C-terminus with a new quencher which was bound to the His6 tagwith nanomolar affinity (Kd ~10-8 M) in the presence of 2 μM NiCl2.