Biophysical characterisation reveals structural disorder in the nucleolar protein, Dribble

• Published in: Biochemical and biophysical research communications Vol. 343; no. 1; pp. 311 - 318
• Main Authors: Yiu, C.-P. Benny, Beavil, Rebecca L., Chan, H.Y. Edwin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 28-04-2006
• Subjects: Amino Acid Sequence; Animals; Biophysical Phenomena; Biophysics; Drosophila; Drosophila melanogaster - metabolism; Drosophila Proteins - biosynthesis; Drosophila Proteins - chemistry; Drosophila Proteins - genetics; Escherichia coli; HRB2; Intrinsically disordered protein; Intrinsically unfolded proteins; K-homology; Krr1p; Molecular Sequence Data; Nuclear Proteins - biosynthesis; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Pfg27; Protein Conformation; RNA - chemistry; RNA binding; RNA-Binding Proteins - biosynthesis; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - genetics; Solvents - chemistry; Pfg27; Intrinsically unfolded proteins; K-homology; Intrinsically disordered protein; HRB2; Krr1p; RNA binding
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2006.02.153

Dribble (DBE) is an essential protein in
Drosophila that belongs to the evolutionarily conserved Krr1p protein family. Proteins in this family are localised in the cell nucleolus and are important for the processing of ribosomal RNAs. However, little is known about their structural and biophysical properties. We have expressed and purified full-length DBE protein from
Escherichia coli. Consistent with the native role of DBE in RNA processing, recombinant DBE was shown to bind RNA homo-polymers in vitro. By bioinformatics, size-exclusion chromatography, equilibrium sedimentation analysis, controlled proteolysis, and a variety of spectroscopic techniques, we have found that DBE is a monomeric protein in solution containing both α- and β-structures. Moreover, the structure of DBE is expanded and significantly disordered (∼45% disordered). Natively disordered proteins are thought to provide a disproportionately large surface area and structural plasticity for nucleic acid binding. We therefore propose that the presence of structural disorder is an important feature of DBE that facilitates the protein to interact with RNAs in the nucleolus.