PCVA also detects residues that are much lower ranked in CSA and FSA. PHE138 and LEU139 are both part of the ligand binding site and obviously have a high electrostatic impact on the substrates. Consequently, PCVA ranks them very high at 12 and 13, respectively, in contrast to FSA (156-163) while CSA also assigns quite high ranks to these residues (24-36). Similar results are observed for TRP142 and LYS143, which also seem to play a role in ligand binding and are ranked on 10 and 11 in PCVA, whereas FSA assigns much lower ranks (17 and 18-155) than CSA (37+).