Rotavirus nonstructural protein NSP2 self-assembles into octamers that undergo ligand-induced conformational changes

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Rotavirus nonstructural protein 2 (NSP2) is crucial for viral replication.
• NSP2 binds single-stranded RNA and exhibits NTPase activity, but its precise function is unknown.
• Previous studies suggested NSP2 forms multimers and may act as a molecular motor.

Purpose of the Study:

• To characterize the solution structure and conformational dynamics of recombinant rotavirus NSP2.
• To investigate the oligomeric state and RNA/ADP binding properties of NSP2.
• To elucidate the functional implications of NSP2's structural characteristics in viral replication.

Main Methods:

• Velocity and equilibrium ultracentrifugation
• Dynamic light scattering
• Circular dichroism spectroscopy

Main Results:

• NSP2 exists predominantly as a functional octamer capable of binding RNA and ADP.
• Magnesium ions induce partial octamer dissociation, which is reversed by ADP and RNA binding.
• ADP and ATP analogues promote a more compact octameric conformation, evidenced by increased sedimentation rates.
• NSP2 possesses a high beta-sheet content, with minor conformational changes induced by magnesium, reversed by RNA.

Conclusions:

• Rotavirus NSP2 functions as an octamer that undergoes conformational changes upon binding ADP and RNA.
• These conformational dynamics support the hypothesis of NSP2 acting as a molecular motor for viral mRNA packaging.
• Understanding NSP2 structure and function provides insights into rotavirus replication mechanisms.