The electrostatic potential of the peptide-binding groove of the B4 haplotype is highly positively-charged, whereas those of the B15 and B19 haplotypes are negatively-charged and that of B12 is neutral (Fig. 6) . The peptide-binding grooves are highly lipophilic in all models (Fig. 7) . The B pockets of the peptide-binding grooves . Verification score plots of the models (plots generated using DS2.5). The verification scores of all residues in B15 were greater than zero, whereas one residue in B12 and B19 and three residues in B4 were less than zero. doi:10.1371/journal.pone.0039344.g002 are more flexible than the F pockets in all structures (Fig. 8) , which suggests that the variation of the anchor residues in the B pocket is greater than in the F pocket.