A theoretical analysis of HLA-DRbeta1*0301-CLIP complex using the first three multipolar moments of the electrostatic field.

Interactions between the HLA-DRbeta1*0301 molecule and several occupying peptides obtained from computational substitutions made to the CLIP peptide are studied. The exploration was carried out using a vector composed of the first three terms of the multipolar expansion of the electrostatic field, namely, charge (q), dipole (d) and quadrupole (C). Comparisons between pocket-peptide interactions established that the binding pockets for this HLA molecule are ordered in terms of their importance for binding peptides, as follows: P1 >>> P4 > P6 > P7 > P9. A set of electrostatically distinct amino acids that determine interaction stability and specificity were identified for each pocket. The beta74R residue was especially identified as being the key amino acid mediating the occupying peptide binding for pocket 4; this residue has been recently associated with Graves' disease.