Mechanisms Contributing to T Cell Receptor Signaling and Assembly Revealed by the Solution Structure of an Ectodomain Fragment of the CD3ϵγ Heterodimer  Zhen-Yu J. Sun, Ki Seok Kim, Gerhard Wagner, Ellis L. Reinherz  Cell  Volume 105, Issue 7, Pages 913-923 (June 2001) DOI: 10.1016/S0092-8674(01)00395-6

Figure 1 Stereo View of the Backbone Trace Ensemble of 15 CD3ϵγext NMR Structures The β strands are labeled (white for CD3ϵ and cyan for CD3γ) and colored in yellow, with the more mobile loop regions colored in red. For clarity, the flexible, mobile, and unstructured 26 amino acid interdomain linker has been omitted. Figure prepared using MOLMOL (Koradi et al., 1996) Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)

Figure 2 Ribbon Diagrams of the CD3ϵγext Molecule Two views of CD3ϵγext are shown in which the linker region and several unstructured residues at the N termini of each domain have been omitted. The structure in (B) is rotated ∼50° about the vertical axis relative to that in (A). The β strands are colored in yellow and labeled (red for CD3ϵ and blue for CD3γ). In (A), three pairs of main chain atoms involved in interdomain G strand hydrogen bonds are designated with amide protons in gray and carbonyl oxygen atoms in red. In (B), the two pairs of disulfide-linked cysteine residues are shown as rods colored in magenta. Figure prepared using MOLMOL (Koradi et al., 1996) Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)

Figure 3 The β Sheet Arrangement for CD3ϵ and CD3γ Extracellular Domains (A) and (B) show the β sheet organization for CD3ϵ and CD3γ, respectively. Single and paired hydrogen bonds between strands (yellow) are identified by single and double arrowhead lines, respectively. The reference point cysteine residues in the B and F strands of each domain which participate in intradomain disulfide bond formation are colored red. The secondary structure of the CD3ϵ segment following the FG turn is ambiguous due to lack of NMR restraints and, therefore, designated as an extended oval. (C) defines the association between the G strands and the abutting stalk regions (shaded pink) indicating juxtaposition of the four cysteine residues (colored green). Note that the highlighted stalk residues in (C) are not contained in the recombinant scCD3ϵγ26 protein Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)

Figure 4 Sequence Alignment of CD3ϵ, γ, and δ Ectodomains Derived from Human, Mouse, Rat, Sheep, and Rabbit Species The residues conserved among virtually all homologs are designated in red letters. Color shading indicates the following: pink—conserved between CDϵ/γ only; orange—conserved between CD3ϵ/δ only; green—conserved between CD3γ/δ only; yellow—homologous between CD3γ/δ only; cyan—conserved among CD3ϵ only. The β strand assignments based on the structures of CD3ϵ and γ, and predictions for CD3δ, are drawn for the mouse sequences. Note that the N-terminal segment of the CD3ϵ G strand is ambiguous and hence not fully shaded Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)

Figure 5 CD3ϵγ Heterodimeric Interface Characterization For the purposes of illustration, the CD3ϵ domains in the left panels and CD3γ domain in the right panels have been rotated ∼180° about the vertical axis relative to each other in an opened book configuration. (A) shows the space filling model of CD3ϵ with residues conserved in CD3ϵ sequences highlighted. (B) shows CD3γ with residues conserved or homologous between CD3γ and δ sequences highlighted. The colors in (A) and (B) indicate hydrophobic and/or aromatic (green) and hydrophilic (pink) residues. (C) and (D) show the molecular surfaces of CD3ϵ and CD3γ, respectively, with the domain interfaces (defined as atoms within 5 Å of their binding partners) colored in green. (E) and (F) show the ribbon diagrams of CD3ϵ and CD3γ, respectively, with the critical residues involved in interdomain interactions shown as ball-and-stick models and labeled in black. The figure was prepared using MOLMOL (Koradi et al., 1996) Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)

Figure 6 Mutational Analysis of CD3ϵ: Role of Interface Residues and Conserved Stalk Region Cysteines in Subunit Association (A) shows the schematic outline of wtCD3γ, wtCD3ϵ, and mutant CD3ϵ molecules with the indicated addition of cytoplasmic C-terminal tags. (B, top) shows ECL analysis of lysate from Cos-7 cells, transfected with the indicated cDNAs and immunoprecipitated (IP) and Western blotted (WB) with the indicated tag-specific mAbs. (B, bottom) shows parallel analysis using the conformationally dependent anti-CD3ϵ mAb, 17A2 Cell 2001 105, 913-923DOI: (10.1016/S0092-8674(01)00395-6)