Viral Genomic RNA Binding:
A key function of the LASV NP is to bind and protect viral genomic RNA forming ribonucleoprotein complexes. The correct formation of these ribonucleoprotein complexes are required for both viral transcription and replication. The proposed site for this binding is a highly positively charged groove found between the C and N domains. In vitro assays confirm that RNA strands can bind between these LASV NP oligomers although the exact length of these oligomers has not yet been accurately determined. These RNP complexes serve to protect the RNA from the RNase enzymes in the environment as well from the exo and endo nuclease activity of the N and L proteins of the Lassa virus. In vitro studies carried out have proved that the genomic RNA is not subject to hydrolysis by the NP exonuclease even under the enzyme’s optimal conditions (Qi et al 2010).
The groove is predicted to contain 9 positively charged amino acid residues from α5, α17, α24 and β12. These amino acids are R58, K86, K110, R118, K162, K167, R329, R551, R556
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| The image shows the proposed positively charged RNA binding groove. Image courtesy of Xiaoxuan et al 2010. Cap binding and Immune Evasion revealed by Lassa nucleoprotein strucutre. Supplementary Information Nature Vol 468 pg 12 Dec 2010 |