PQBP3/NOL7 is an intrinsically disordered protein.

PQBP3 is a protein binding to polyglutamine tract sequences that are expanded in a group of neurodegenerative diseases called polyglutamine diseases. The function of PQBP3 was revealed recently as an inhibitor protein of proteasome-dependent degradation of Lamin B1 that is shifted from nucleolus to peripheral region of nucleus to keep nuclear membrane stability. Here, we address whether PQBP3 is an intrinsically disordered protein (IDP) like other polyglutamine binding proteins including PQBP1, PQBP5 and VCP. Multiple bioinformatics analyses predict that N -terminal region of PQBP3 is unstructured. High-speed atomic force microscopy (HS-AFM) reveals that N -terminal region of PQBP3 is dynamically changed in the structure consistently with the predictions of the bioinformatics analyses. These data support that PQBP3 is also an IDP. • This study addresses whether PQBP3/NOL7 is an intrinsically disordered protein. • IUPred2A predicts N -terminal region of PQBP3/NOL7 unstructured. • AlfaFold2 also predicts N -terminal region of PQBP3/NOL7 unstructured. • HS-AFM reveals N -terminal region of PQBP3 to change dynamically in the structure. [ABSTRACT FROM AUTHOR]