Kozłowska, M., Tarczewska, A., Jakób, M., Bystranowska, D., Taube, M., Kozak, M., Czarnocki-Cieciura, M., Dziembowski, A., Orłowski, M., Tkocz, K., Ożyhar, A. (2017). Nucleoplasmin-like domain of FKBP39 from Drosophila melanogaster forms a tetramer with partly disordered tentacle-like C-terminal segments.  Sci. Rep. 7(): 40405.

FBrf0234506

Research paper

Nucleoplasmins are a nuclear chaperone family defined by the presence of a highly conserved N-terminal core domain. X-ray crystallographic studies of isolated nucleoplasmin core domains revealed a β-propeller structure consisting of a set of five monomers that together form a stable pentamer. Recent studies on isolated N-terminal domains from Drosophila 39-kDa FK506-binding protein (FKBP39) and from other chromatin-associated proteins showed analogous, nucleoplasmin-like (NPL) pentameric structures. Here, we report that the NPL domain of the full-length FKBP39 does not form pentameric complexes. Multi-angle light scattering (MALS) and sedimentation equilibrium ultracentrifugation (SE AUC) analyses of the molecular mass of the full-length protein indicated that FKBP39 forms homotetrameric complexes. Molecular models reconstructed from small-angle X-ray scattering (SAXS) revealed that the NPL domain forms a stable, tetrameric core and that FK506-binding domains are linked to it by intrinsically disordered, flexible chains that form tentacle-like segments. Analyses of full-length FKBP39 and its isolated NPL domain suggested that the distal regions of the polypeptide chain influence and determine the quaternary conformation of the nucleoplasmin-like protein. These results provide new insights regarding the conserved structure of nucleoplasmin core domains and provide a potential explanation for the importance of the tetrameric structural organization of full-length nucleoplasmins.

PMC5225439 (PMC) (EuropePMC)