The T-cell receptor complex with TCR-α and TCR-β chains, CD3 and ζ-chain accessory molecules and the co-receptor CD4

In immunology, the CD3 antigen (CD stands for cluster of differentiation) is a protein complex composed of four distinct chains (CD3γ, CD3δ and two times CD3ε) in mammals, that associate with molecules known as the T cell receptor (TCR) and the ζ-chain to generate an activation signal in T lymphocytes. The Entrez Global Query Cross-Database Search System is a powerful Federated search engine or Web portal that allows users to search many discrete Health sciences The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The Protein Data Bank ( PDB) is a repository for 3-D structural data of Proteins and Nucleic acids These data typically obtained by X-ray crystallography The National Center for Biotechnology Information ( NCBI) is part of the United States National Library of Medicine (NLM a branch of the National Institutes Swiss-Prot is a manually curated Biological database of Protein sequences In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Chromosome 11 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome CD3e molecule epsilon (CD3-TCR complex, also known as CD3E, is a human gene and protein a part of CD3 protein complex CD3e molecule epsilon (CD3-TCR complex, also known as CD3E, is a human gene and protein a part of CD3 protein complex The Entrez Global Query Cross-Database Search System is a powerful Federated search engine or Web portal that allows users to search many discrete Health sciences The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The National Center for Biotechnology Information ( NCBI) is part of the United States National Library of Medicine (NLM a branch of the National Institutes Swiss-Prot is a manually curated Biological database of Protein sequences In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Chromosome 11 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome CD3g molecule gamma (CD3-TCR complex, also known as CD3G, is a human Gene. CD3g molecule gamma (CD3-TCR complex, also known as CD3G, is a human Gene. The Entrez Global Query Cross-Database Search System is a powerful Federated search engine or Web portal that allows users to search many discrete Health sciences The Human Genome Organisation (HUGO is an organization involved in the Human Genome Project, a project about mapping the human genome The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The National Center for Biotechnology Information ( NCBI) is part of the United States National Library of Medicine (NLM a branch of the National Institutes Swiss-Prot is a manually curated Biological database of Protein sequences In the fields of Genetics and Evolutionary computation, a locus (plural loci) is a fixed position on a Chromosome such as the position of a Chromosome 11 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response The cluster of differentiation (often abbreviated as CD) is a protocol used for the identification and investigation of Cell surface molecules present on Leukocytes CD3g molecule gamma (CD3-TCR complex, also known as CD3G, is a human Gene. CD3d molecule delta (CD3-TCR complex, also known as CD3D, is a human Gene. CD3e molecule epsilon (CD3-TCR complex, also known as CD3E, is a human gene and protein a part of CD3 protein complex The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells that is in general responsible for recognizing Antigens bound T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity.

The TCR, ζ-chain and CD3 molecules together comprise the TCR complex.

The CD3γ, CD3δ and CD3ε chains are highly related cell surface proteins of the immunoglobulin superfamily containing a single extracellular immunoglobulin domain. The immunoglobulin superfamily (IgSF is a large group of cell surface and soluble proteins that are involved in the recognition binding or adhesion processes of cells In Cell biology, Molecular biology and related fields the word extracellular (or sometimes extracellular space) means "outside the cell

The transmembrane region of the CD3 chains is negatively charged, a characteristic that allows these chains to associate with the positively charged TCR chains (TCRα and TCRβ).

The intracellular tails of the CD3 molecules contain a single conserved motif known as an immunoreceptor tyrosine-based activation motif or ITAM for short, which is essential for the signaling capacity of the TCR. An immunoreceptor tyrosine-based activation motif (ITAM is a conserved sequence of four Amino acids that is repeated twice in the cytoplasmic tails of certain cell surface proteins

Phosphorylation of the ITAM on CD3 renders the CD3 chain capable of binding an enzyme called ZAP70 (zeta associated protein), a kinase that is important in the signaling cascade of the T cell. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins ZAP-70 is an abbreviation for Zeta-chain-associated protein kinase 70 (70 is the molecular weight in KDa) In Chemistry and Biochemistry, a kinase, alternatively known as a phosphotransferase, is a type of Enzyme that transfers Phosphate

References

• Cellular and Molecular Immunology (5th Ed. ) Abbas AK, and Lichtman, Editor: Saunders, Philadelphia, 2003.

External links

• MeSH CD3+Antigens