Recognition mechanism of an intrinsically disordered antigen by a monoclonal antibody.

MARISOL FASSOLARI, MARÍA LAURA CERUTTI, LUCÍA CHEMES, CLARA SMAL, ANGELES HEER AND GONZALO DE PRAT GAY

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Congreso; 3rd Latin American Protein Society meeting; 2010

Persistent infections by high-risk human papillomaviruses (HPV) are the main etiologic factors for cervical cancer. The major cell transforming activity of HPVs is the E7 oncoprotein. HPV16 E7 is an extended dimer with a conserved N-terminal intrinsically disordered domain and a globular C-terminal domain. E7 represents an interestingmodel to investigate the recognition mechanism of intrinsically disordered antigens by antibodies. Here, we present a characterization of the interaction between E7 and the specific M1 monoclonal antibody. Spectroscopic solution binding experiments indicate high binding affinity. Fragmentation analysis of E7 shows that M1 recognizes an epitope comprising amino acids 36-48. Kinetic studies between M1 and E736-48 suggest two phases in complexformation: a fast protein-concentration bimolecular association phase (kon 1.108 M-1 seg-1) and a slow protein concentration independent phase (kobs 4.10-3 S-1). Circular dichroism experiments indicated conformational changes induced by the binding corresponding to the slow phase observed in kinetic experiments. The equilibrium dissociation constant of M1 for the E736-48 peptide is 6-fold higher than that measured for full length E7. This result suggests that the highest affinity recognition by the M1 requires entire E7. This study shows the recognition mechanism of a unique epitope, located between the N-terminal and the C-terminal regions of E7, by a monoclonal antibody.