Viral proteins targeted by antiviral agents. (A) HIV-1 reverse transcriptase in complex with dsDNA and the NRTI emtricitabine triphosphate (PDB code: 6OTZ). (B) HCV NS5B polymerase targeted by GS-639476 (5UJ2). (C) HCMV DNA polymerase targeted by foscarnet (3KD5). (D) Influenza B virus polymerase in complex with viral RNA (6QCT). (E) HSV polymerase (2GV9, 4M3R). (F) HIV-1 integrase tetramer targeted by raltegravir (5U1C, 3L2V). (G) HIV-1 protease dimer targeted by darunavir (3OY4). (H) HCV NS3 protease targeted by the MK-5172 analog (5EQQ). (I) HCV NS5A dimer structure (4CL1). (J) Influenza A matrix 2 protein targeted by rimantadine (6BKL). (K) HIV-1 Env glycoprotein in the trimeric form of gp120 and gp41 (6OT1). (L) Influenza A virus hemagglutinin targeted by Arbidol (5T6N). (M) Influenza A neuraminidase targeted by peramivir (4MWV). Drug binding pockets are indicated by red circles. Protein structures were visualized using the software PyMOL V2.1 (http://www.pymol.org/).