TY - JOUR
T1 - Two structural states of complexes of peptide and class II major histocompatibility complex revealed by photoaffinity-labeled peptides
AU - Carrasco-Marín, Eugenio
AU - Petzold, Shirley
AU - Unanue, Emil R.
PY - 1999/10/29
Y1 - 1999/10/29
N2 - The complex of the murine class II histocompatibility molecules I-A(k) with high affinity binding peptides were resistant to denaturation when examined by SDS-polyacrylamide gel electrophoresis at various pH levels. In contrast, complexes made with low affinity binding peptides were highly sensitive to denaturation by SDS. This effect was more pronounced at low pH. Placing a photoactivatable probe at the amino terminus of the peptides resulted in their covalent linkage to soluble I-A(k) molecules. We found an inverse relationship between the capacity of peptides to form SDS-stable complexes with I-A(k) and their extent of covalent association with either the α or β chain. The relationship held true for three different peptides in which the main anchor residues were changed so as to affect their binding affinity for I-A(k) molecules. Thus, high affinity peptides generate a complex in which the motion of their amino termini was restricted, whereas complexes of low affinity peptides are more flexible. In agreement with this observation, complexes of I-A(k) with high affinity peptides were highly resistant to proteolysis, in contrast to those formed with weakly binding peptides, which were more likely to be cleaved. Complexes with low affinity peptides generate a structure with enhanced flexibility as compared with complexes with high affinity peptides.
AB - The complex of the murine class II histocompatibility molecules I-A(k) with high affinity binding peptides were resistant to denaturation when examined by SDS-polyacrylamide gel electrophoresis at various pH levels. In contrast, complexes made with low affinity binding peptides were highly sensitive to denaturation by SDS. This effect was more pronounced at low pH. Placing a photoactivatable probe at the amino terminus of the peptides resulted in their covalent linkage to soluble I-A(k) molecules. We found an inverse relationship between the capacity of peptides to form SDS-stable complexes with I-A(k) and their extent of covalent association with either the α or β chain. The relationship held true for three different peptides in which the main anchor residues were changed so as to affect their binding affinity for I-A(k) molecules. Thus, high affinity peptides generate a complex in which the motion of their amino termini was restricted, whereas complexes of low affinity peptides are more flexible. In agreement with this observation, complexes of I-A(k) with high affinity peptides were highly resistant to proteolysis, in contrast to those formed with weakly binding peptides, which were more likely to be cleaved. Complexes with low affinity peptides generate a structure with enhanced flexibility as compared with complexes with high affinity peptides.
UR - http://www.scopus.com/inward/record.url?scp=0033615531&partnerID=8YFLogxK
U2 - 10.1074/jbc.274.44.31333
DO - 10.1074/jbc.274.44.31333
M3 - Article
C2 - 10531333
AN - SCOPUS:0033615531
VL - 274
SP - 31333
EP - 31340
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 44
ER -