Dengue virus 2 non-structural protein NS5 complexed with RNA, molecular model. The non-structural protein 5 (NS5) is the largest of the Dengue virus non-structural proteins, functioning as both an RNA-dependent RNA polymerase (RdRp) that replicates the viral RNA and an RNA methyltransferase enzyme (MTase) that protects the viral genome by RNA capping. The image shows NS5 (purple) complexed with an 30-mer RNA (green) and an 9-mer RNA (red).