Solution structures of DEAD-box RNA chaperones reveal conformational changes and nucleic acid tethering by a basic...

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Mitochondrial DEAD-box proteins Mss116p and CYT-19 are ATP-dependent helicases.
• These proteins function as general RNA chaperones.
• The structural role of their C-terminal extensions and basic tails is not well understood.

Purpose of the Study:

• To determine the solution structures of full-length Mss116p and CYT-19 and their deletion mutants.
• To elucidate the structural role of the basic tails in RNA chaperone activity.

Main Methods:

• Small-angle X-ray scattering (SAXS) was used to obtain solution structures.
• Analysis of complexes with full-length proteins, deletion mutants, and chimeric oligonucleotides.

Main Results:

• The two core domains exhibit a preferred relative orientation in an open state without substrates.
• Protein structures transition to a compact closed state upon binding RNA and adenosine nucleotide.
• Basic tails are flexibly attached, enabling binding to duplex DNA segments in various directions.

Conclusions:

• The basic tails of DEAD-box proteins contribute to RNA chaperone activity.
• Flexible binding of basic tails to RNA substrates enhances the unwinding of neighboring duplexes.