Question

hi IMMMUNOLOGY question

Can someone sum up and explain to me the structure of (b) & (c) in the picture? what are the structures lf the receptors in (c) ?

NH, NH, B CDR3B CDR1 CDR2B CDR3 CDR1B 34 140 201 Disulfide bond - 2225-5-255 Transmembrane domain Intracellular- COOH COOH domain (248) (282) Figure 3-15 Ruby Immunology, Eighth Edition 2019 W. H. Freeman and Company 41 of 51

Answer 1

These figures are of TCRs (T Cell Receptors) on T cell membrane. TCRs bind to antigens presented by MHC class I proteins. Figure (a) shows the TCR in linear form with specific disulfide bonds. The protein consists of 2 chains, alpha and beta chains, which are held by a lower disulfide bond. Both chains are divided into V (variable) and C (Constant) regions.

Figure (b) also shows the same TCR protein, but as a Ribbon diagram. This is the same TCR as in figure (a). This figure marks the variable regions (V$\alpha$ and V$\beta$ regions) and the constant regions (C$\alpha$ and C$\beta$ regions) for both alpha and beta chains.

If looked closely, some of the upper portions of the V$\alpha$ and V$\beta$ regions of figure (b) is marked in red. These regions are zoomed in and marked in detail in figure (c). These are the CDR (Complementarity determining regions) regions. These regions occur in the variable part of both the chains and are responsible for specific binding to specific antigens. Both alpha and beta chains have three CDR regions (marked as CDR 1 to 3).