Analysis of the structure of empty and peptide-loaded major histocompatibility complex molecules at the cell surface.
We compared the conformation of empty and peptide-loaded class I major histocompatibility complex (MHC) molecules at the cell surface. Molecular conformations were analyzed by fluorescence resonance energy transfer (FRET) between fluorescent-labeled Fab fragments bound to the alpha 2 domain of the MHC heavy chain and fluorescent-labeled Fab fragments bound to beta 2-microglobulin. No FRET was found between Fab fragments bound to empty H-2Kb, but FRET was detected when empty H-2Kb molecules were loaded with peptide. The magnitude of FRET depended on the sequence of the peptide used. The results imply that empty H-2Kb molecules are in a relatively extended conformation, and that this conformation becomes more compact when peptide is bound. These changes, which are reflected in peptide-dependent binding of monoclonal antibodies, affect the surfaces of MHC molecules available for contact with T cell receptors and hence may influence T cell-receptor recognition of MHC molecules.
Catipović
B
B
Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21224.
Talluri
G
G
Oh
J
J
Wei
T
T
Su
X M
XM
Johansen
T E
TE
Edidin
M
M
Schneck
J P
JP
D000818:Animals; D002460:Cell Line; D000939:Epitopes; D005453:Fluorescence; D006183:H-2 Antigens / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D051379:Mice; D010047:Ovalbumin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D001613:beta 2-Microglobulin / Q000378:metabolism
D000939:Epitopes; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D010446:Peptide Fragments; D010455:Peptides; D001613:beta 2-Microglobulin; D010047:Ovalbumin