Thermodynamic stability of HLA-B*2705. Peptide complexes. Effect of peptide and major histocompatibility complex protein mutations.
Designing synthetic vaccines from class I major histocompatibility complex (MHC)-binding antigenic peptides requires not only knowledge of the binding affinity of the designed peptide but also predicting the stability of the formed MHC-peptide complex. In order to better investigate structure-stability relationships, we have determined by circular dichroism spectroscopy the thermal stability of a class I MHC protein, HLA-B*2705, in complex with a set of 39 singly substituted peptide analogues. The influence of two anchoring side chains (P3 and P9) was studied by peptide mutation and appropriate site-directed mutagenesis of the HLA-B*2705 binding groove. The side chain at P9 is clearly the one that contributes the most to the thermal stability of the MHC-peptide complexes, as destabilization up to 25 degrees C are obtained after P9 mutation. Interestingly, structure-stability relationships do not fully mirror structure-binding relationships. As important as the C-terminal side chain are the terminal ammonium and carboxylate groups. Removal of a single H-bond between HLA-B27 and the terminal peptide moieties results in thermal destabilization up to 10 degrees C. Depending on the bound peptide and the location of the deleted H-bond, the decrease in the thermal stability of the corresponding complex is quantitatively different. The present study suggests that any peptidic amino acid at positions 3 and 9 promotes refolding of the B27-peptide complex. Once the complex is formed, the C-terminal side chain seems to play an important role for maintaining a stable complex.
Dédier
S
S
Department of Applied BioSciences, Swiss Federal Institute of Technology, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. didier@pharma.ethz.ch
Reinelt
S
S
Reitinger
T
T
Folkers
G
G
Rognan
D
D
D001483:Base Sequence; D002942:Circular Dichroism; D017931:DNA Primers; D015235:HLA-B Antigens / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D009154:Mutation; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013816:Thermodynamics
D017931:DNA Primers; D015235:HLA-B Antigens; D010455:Peptides