β1-adrenergic Receptor Solubilized in the Form of Nanodiscs: Screening of Various Amphipatic Polymers

The development of a reliable and easily used diagnostic test for measuring autoantibodies to ?1-adrenergic receptor (?1ADR Ab) in patient blood is an unmet clinical need. The enzyme-linked immunosorbent assay (ELISA) is considered as the most appropriate method for this task. In ELISA, the use of peptides corresponding to various fragments of amino acid sequence of ?1ADR as antigens leads to inadequate results as β1ADR Ab appear to recognize conformationally dependent epitopes that are generated during the formation of unique tertiary structure of the receptor. Isolation of ?1ADR preserving the native conformation and functional characteristics is a quite challenging task. A promising approach to address this task is the use of amphipatic polymers capable of forming nanodiscs, it permits to successfully solubilize membrane proteins. In order to obtain the preparations of solubilized β1ADR that can be used as antigens in ELISA we have tested 17 various amphipatic polymers. The best relative solubilization values (RSV) were obtained using UltrasoluteTM Amphipol 17 (87%) and 18 (62%), as well as by AASTY 11-45 (76%), 11-50 (77%) and 6-50 (78.5%).