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Table 1 Specificity pockets defined by interactions with sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) drugs in three-dimensional computer models of the M.tb dimer, M.tb monomer and crystal structure complexes of human phosphodiesterase 5 enzyme

From: Three-dimensional models of Mycobacterium tuberculosis proteins Rv1555, Rv1554 and their docking analyses with sildenafil, tadalafil, vardenafil drugs, suggest interference with quinol binding likely to affect protein’s function

Protein Sildenafil (Viagra) Tadalafil (Cialis) Vardenafil (Levitra)
M.tb dimer model (Rv1554) Phe22, Arg25, Glu26, Trp83, Ser86, Ala87, Arg89, Ala90 Phe22, Arg25, Glu26, Trp83, Ser86, Ala87, Arg89, Ala90 Ser18, Arg21, Phe22, Arg25, Glu26, Trp83, Ser86, Arg89
(Rv1555) QP site Trp20, Phe23, Ser24, His84, Arg85, Phe88 Trp20, Phe23, Ser24, His84, Arg85, Phe88 Trp20, Phe23, His84, Arg85, Phe88
M.tb monomer model (Rv1555) QD site Val33, Val36, Leu37, Leu40, Phe41, Leu58, Val70, Val71, Leu74, Met121 Val36, Leu37, Leu38, Leu40, Phe41, Leu58, Val62, Val71, Leu74, Val75, Met121 Val33, Val36, Leu37, Leu38, Leu40, Phe41, Leu58, Val70, Val71, Leu74, Val75, Met121
Crystal structures of human PDE5 -drug complexes (1UDT– VIA) Tyr612,His613,Asn661, Tyr664,Ile768,Ala779, Val782,Ala783,Leu804, Met816,Gln817, Gly819, Phe820 (1UDU– CIA) Tyr612,Ser663,Val782,Ala783, Phe786,Phe787, Leu804,Ile813, Met816, Gln817, Phe820 (1UHO– VDN) Tyr612,His613,Tyr664, Ala779, Ala783,Phe786, Leu804, Met816, Gln817, Gly819, Phe820
  1. Note: Amino acid residues common to all three drug binding pockets are shown in bold. The residue numbering is in sequential order for M.tb proteins and according to numbering in crystal structure complex for human PDE5 protein as in PDB codes:1UDT, 1UDU, 1UHO for sildenafil, tadalafil, vardenafil, respectively