Y sil y enh
FIGURE 8-7 Germline organization of human TCR loci. The human TCR p, a, y, and 8 chain loci are shown, as indicated. Exons and introns are not drawn to scale, and nonfunctional pseudogenes are not shown. Each C gene is shown as a single box but is composed of several exons, as illustrated for Cp1. Gene segments are indicated as follows: L, leader (usually called signal sequence); V, variable; D, diversity; J, joining; C, constant; enh, enhancer; sil, silencer (sequences that regulate TCR gene transcription).
contained within the TCR a locus (Fig. 8-7). Each germline TCR locus includes V and J gene segments, the latter being just upstream of C region exons in each locus. In addition, TCR p and TCR 8 loci also have D segments, like the Ig heavy chain locus. At the 5' end of each of the TCR loci, there is a cluster of several V gene segments, arranged in a very similar way to the Ig V gene segments. Upstream of each TCR V gene is an exon that encodes a leader peptide, and upstream of each leader exon is a promoter for each V gene.
In each TCR locus, similar to the Ig loci, C region genes are located just 3' of the J segments. There are two C genes in each of the human TCR p (Cp) and TCR y (Cy) loci and only one C gene each in the TCR a (Ca) and TCR 8 (C8) loci. Each TCR C region gene is composed of four exons encoding the extracellular C region Ig-like domain, a short hinge region, the transmembrane segment, and the cytoplasmic tail. The TCR p and TCR 8 chain loci resemble the Ig heavy chain locus and contain D segments between V genes and J segments. Each human TCR C gene has its own associated 5' cluster of J segments. In the TCR a or y chains (which are analogous to Ig light chains), the V domain is encoded by the V and J exons; and in the TCR p and 8 proteins, the V domain is encoded by the V, D, and J gene segments.
The relationship of the TCR gene segments and the corresponding portions of TCR proteins that they encode is shown in Figure 8-6B. As in Ig molecules, the TCR V
and C domains assume an Ig fold tertiary structure, and thus the TCR is a member of the Ig superfamily of proteins.
Was this article helpful?
All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.