Figure 1.
Molecular dynamics of ZAP-70 mutants with reduced affinity for CD3ζ chain. (A) Structure of ZAP-70 tandem SH2 domains (cyan) and CD3ζ pITAM (red) chain (left), and affinity between CD3ζ phosphorylated ITAM and indicated mutants of ZAP-70 measured by BIACORE (right). Phospho-tyrosine residues (red sticks) of CD3ζ ITAM, PTB residues (blue sticks), and mutated residues (W163, H165; blue sticks) of ZAP-70 are also shown. Insets show measured distances (dotted lines) between the ITAM phospho-tyrosine (pY15) and the inter-SH2 PTB residues (DI) and between pY4 and the carboxy-terminal PTB residues (DC). KD = kd/ka. (B) Representative snapshots from MD simulations (between 13 and 18 ns) on CD3ζ pITAM (red) and ZAP-70 tandem SH2 domains (blue) with indicated mutations. Phospho-tyrosines of CD3ζ and PTB residues of ZAP-70 are also shown (sticks). See also Videos 1, 2, 3, and 4. (C) Distributions of measured distances between the CD3ζ ITAM phospho-tyrosine (pY15) and the inter-SH2 PTB residues of ZAP-70 (DI), and between CD3ζ ITAM pY4 and the carboxy-terminal PTB residues of ZAP-70 (DC). DI and DC distances for WT, H165A, W163C, and W163A mutants are shown as log f(DI, DC). The boundary of the WT DI/DC distribution is indicated with a dotted line.