TABLE 3

Hydrogen bonds and hydrophobic, cation-π, and π-π interactions formed between arginine or phenylalanine and residues of the substrate-binding site of either AdiC or Gap1 in the outward-open-occluded conformationa

Amino acid substrate locationAdiCb, Arg substrateGap1 3D model
Arg substratePhe substrate
Protein residue backboneProtein residue side chainProtein residue backboneProtein residue side chainProtein residue backboneProtein residue side chain
Backbone
    NH3+HBc Ile23 (TM1)HB Phe294 (TM6)HB Phe294 (TM6)
HB Trp202 (TM6)HB Ser295 (TM6)HB Ser295 (TM6)
HB Ile205 (TM6)HB Ala297 (TM6)HB Ala297 (TM6)
    COOHB Gly27 (TM1)HB Ser26 (TM1)HB Gly106 (TM1)
HB Gly107 (TM1)HB Gly107 (TM1)
Side chain
    CH2PHOBd Trp202 (TM6)PHOB Phe294 (TM6)PHOB Phe294 (TM6)
    GuanidiniumHB Ala96 (TM3)HB Asn101 (TM3)HB Gln178 (TM3)
HB Cys97 (TM3)HB Ser357 (TM10)HB Glu301 (TM8)
Cation-π Trp293 (TM8)Cation-π Trp179 (TM3)
    Aromatic ringπ-π Trp179 (TM3)
  • a See the text.

  • b Protein Data Bank (PDB) ID, 3L1L.

  • c HB, hydrogen bond.

  • d PHOB, hydrophobic.