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Crystallographic Analysis of Rotavirus NSP2-RNA Complex Reveals Specific Recognition of 5'-GG Sequence for RTPase activityCrystallographic Analysis of Rotavirus NSP2-RNA Complex Reveals Specific Recognition of 5'-GG Sequence for RTPase activity
Structural highlights
Function[NSP2_ROTSR] Involved in genome replication and packaging. Plays a crucial role, together with NSP5, in the formation of virus factories (viroplasms) which are large inclusions in the cytoplasm where replication intermediates are assembled and RNA replication takes place. Displays ssRNA binding, NTPase, RNA triphosphatase (RTPase) and ATP-independent helix-unwinding activity activities. The unwiding activity may prepare and organize plus-strand RNAs for packaging and replication by removing interfering secondary structures. Unlike typical helicases, NSP2 requires neither a divalent cation nor a nucleotide energy source for helix destabilization. The RTPase activity may account for the absence of the 5'-terminal gamma-phosphate on the minus-strands of dsRNA genome segments (By similarity). Publication Abstract from PubMedRotavirus non-structural protein NSP2, a functional octamer, is critical for the formation of viroplasms, which are exclusive sites for replication and packaging of segmented double-stranded RNA (dsRNA) rotavirus genome. As a component of replication intermediates, NSP2 is also implicated in various replication-related activities. In addition to sequence-independent single-stranded RNA binding and helix-destabilizing activities, NSP2 exhibits monomer-associated nucleoside and 5' RNA triphosphatase (NTPase/RTPase) activities which are mediated by a conserved H225 residue within a narrow enzymatic cleft. Lack of a 5' gamma-phosphate is a common feature of the (-)RNA of the packaged dsRNA segments in RV. Strikingly, all (-)RNAs (in group A RV) have a 5' GG dinucleotide sequence. As the only rotavirus protein with 5' RTPase activity, NSP2 is implicated in the removal of the gamma-phosphate from the rotavirus minus-strand RNA. To understand how NSP2, despite its sequence-independent RNA binding property, recognizes minus-strand RNA to hydrolyze the gamma-phosphate within the catalytic cleft, we determined a crystal structure of NSP2 in complex with the 5' consensus sequence of minus-strand rotavirus RNA. Our studies show that the 5' GG of the bound oligoribonucleotide interacts extensively with highly conserved residues in the NSP2 enzymatic cleft. While these residues provide GG-specific interactions, surface plasmon resonance studies suggest that the C-terminal helix and other basic residues outside the enzymatic cleft account for sequence-independent RNA binding of NSP2. A novel observation from our studies, which may have implications in viroplasm formation, is that the C-terminal helix of NSP2 exhibits two distinct conformations and engages in domain swapping interactions, which result in the formation of NSP2 octamer chains. Crystallographic Analysis of Rotavirus NSP2-RNA Complex Reveals Specific Recognition of 5' -GG Sequence for RTPase activity.,Hu L, Chow DC, Patton JT, Palzkill T, Estes MK, Prasad BV J Virol. 2012 Jul 18. PMID:22811529[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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