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Figure 4.
Figure 4. Conformational Change in the Cα Domain that May
Relate to a Conformational Switch for Intracellular Signaling in
T Cells(A) The acidic ectodomain of CD3ε has been proposed to
interact with the exposed electropositive surface of the A, B,
E, and D strands of the Cβ domain shown in light green
(Ghendler et al. 1998; Sun et al. 2001 and Wang et al. 1998).
This cavity is bordered by the F-G loop of the Cβ domain.
Conformational changes between unliganded (cyan) and liganded
(red) states of this region are shown. Positively charged side
chains (K121, K132, K136, K184, R190, and R230) projecting from
Cα and Cβ are thought to further stabilize the docking of
CD3ε into this cavity (Sun et al., 2001). Cα Lys132 swings
toward the cavity upon ligation of LC13 while the whole of the
A-B loop shifts to enlarge the cavity in the liganded
complex.(B) Comparison of A-B loop structure in a number of
different TCRs. Color coding of the A-B loop is as follows:
unliganded LC13, cyan; liganded LC13, red; 2C, blue; A6 weak
agonist, green; and the partially built loop of the B7 TCR,
orange. The N15 A-B loop structure is not shown but resembles
the 2C structure.
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