The white blood cells known as T lymphocytes respond to antigens thatbind specifi cally to the T cell receptor, which consists of an antigen-binding αβ transmembrane protein as well as a set of transmembrane signaltransducing proteins known as CD3 that are targets of NRTKs. Thecytoplasmic domains of the CD3 proteins are positively charged and, in the absence of antigen, interact with the intracellular surface of the plasma membrane in such a way that buries several of their Tyr residues in the lipidbilayer. Antigen binding to the T cell receptor leads to a localized infl ux ofCa2+ ions. (a) Explain how a high concentration of Ca2+ could promote phosphorylation and activation of the CD3 proteins. (b) Would this henomenon make the T lymphocyte more or less responsive to the antigen?
The white blood cells known as T lymphocytes respond to antigens that
bind specifi cally to the T cell receptor, which consists of an antigen-binding αβ transmembrane protein as well as a set of transmembrane signaltransducing proteins known as CD3 that are targets of NRTKs. The
cytoplasmic domains of the CD3 proteins are positively charged and, in the absence of antigen, interact with the intracellular surface of the plasma
membrane in such a way that buries several of their Tyr residues in the lipid
bilayer. Antigen binding to the T cell receptor leads to a localized infl ux of
Ca2+ ions. (a) Explain how a high concentration of Ca2+ could promote
phosphorylation and activation of the CD3 proteins. (b) Would this henomenon make the T lymphocyte more or less responsive to the antigen?
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