Kinetic evidence for a ligand-binding-induced conformational transition in the T cell receptor.
Thermodynamics and kinetics of the interaction between T cell receptor specific for cytomegalovirus peptide (TCR(CMV)) and its specific ligand, pp65-HLA-A*0201 complex, were studied by surface plasmon resonance and stopped-flow methods. In the latter measurements, fluorescence resonance energy transfer (FRET) between fluorescently labeled reactants was used. Thermodynamic data derived from surface plasmon resonance measurements suggest that the complex formation is driven by both favorable enthalpy and entropy. Two reaction phases were resolved by the stopped-flow measurements. The rate constant of the first step was calculated to be close to the diffusion-controlled limit rate (3x10(5) to 10(6) M(-1) s(-1)), whereas the second step's reaction rate was found to be concentration independent and relatively slow (2-4 s(-1) at 25 degrees C). These findings strongly suggest that the interactions between the TCR and its ligand, the peptide-MHC complex, proceed by a two-step mechanism, in which the second step is an induced-fit process, rate determining for antigen recognition by TCR.
Gakamsky
Dmitry M
DM
Department of Immunology, Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel.
Lewitzki
Erwin
E
Grell
Ernst
E
Saulquin
Xavier
X
Malissen
Bernard
B
Montero-Julian
Felix
F
Bonneville
Marc
M
Pecht
Israel
I
D031541:Fluorescence Resonance Energy Transfer; D015234:HLA-A Antigens / Q000737:chemistry*; D015789:HLA-A2 Antigen; D006801:Humans; D007700:Kinetics; D008024:Ligands; D010750:Phosphoproteins / Q000737:chemistry*; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry*; D020349:Surface Plasmon Resonance; D013816:Thermodynamics; D014763:Viral Matrix Proteins / Q000737:chemistry*
D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D008024:Ligands; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; D014763:Viral Matrix Proteins; C065418:cytomegalovirus matrix protein 65kDa