Fig. 4
Secondary structure-guided sequence alignment of the human PX domains. Amino acid sequence alignment of the human PX domains guided by secondary structure predictions defined by PRALINE51. Where available, the precision of the sequence alignments was also manually curated by structural comparisons of the PX domains. As a reference, the secondary structure elements from the crystal structure of the PX domain of p40phox are indicated at the top. The four critical residues involved in canonical phosphoinositide (PtdIns3P) recognition are shown in blue. The noncanonical phosphoinositide-binding residues are highlighted in magenta. These include either a His or Tyr at the first position within helix α1, followed by a stretch of basic Lys/Arg residues leading to the polyproline loop containing the ΨPxxPxK sequence motif (Ψ = hydrophobic side chain)
