TCR ( seen here in a ternary complex …)

TCR’s come in two flavors…

TCR’s (like Ig’s) have immense diversity

5461 ? ? ? ? ? ? ? ? ? = 5461 (2 2 ) 0 + (2 2 ) 1 + (2 2 ) 2 + (2 2 ) 3 + (2 2 ) 4 + (2 2 ) 5 + (2 2 ) 6 = = 5461

“CD3” two heterodimers & one homodimer… specifically:     ( a variant…  is obtained by alternative splicing of the  template )

“CD3” All of the CD3 proteins have a negative charge (aspartic acid) in the transmembrane helix. Interacts with positive charge in the TCR transmembrane component. All CD3 proteins have ITAM (immunoreceptor tyrosine activation motifs) recognized by tyrosine kinases. ( Members of the larger MIRR [multi chain immune recognition receptor] class.)

“CD3” gamma, delta, and epsilon are members of the immunoglobulin superfamily. Each chain has an immunoglobulin domain + a transmembrane component + a cytoplasmic tail (approximately 44 to 55 amino acids long) 90% of chains with zeta are homodimers. Zeta and eta have 9 aa external domains, a transmembrane component and a cytoplasmic tail of 113 aa in zeta and 155 aa in eta; the two variants are transcripts of a common gene; the transcripts are alternatively spliced.

CD 4 & CD8 A heterodimer (usually  sometimes  ) One immunoglobulin domain “small” glycoproteins (30 – 38 kDa) -S—S- + transmembrane component + cytoplasmic tail (25-27 residues) 55 kDa monomeric glycoprotein Four immunoglobulin domains + a transmembrane component + a long cytoplasmic domain (with three serine residues)

CD4 and MHC-II The length of immunoglobulin folds in CD4 is equal to the two immunoglobulin folds in a TCR plus the peptide binding domain in MHC-II and the proximal immunoglobulin fold in MHC-II. Thus, these components can associate. Specifically, the most distal immunoglobulin fold of CD4 associates with the $2 immunoglobulin fold of MHC-II.

CD4 and MHC-II

Other molecules Lots of them… and, they’re important too!

Other molecules