The CD40L is a type II membrane protein and is a member of the tumor necrosis factor (TNF) superfamily of proteins.
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|Synonym:||CD154, gp39, T-BAM|
|MW (calculated):||42,461 daltons|
|MW (SDS-PAGE):||45 Kd|
|Abs 0.1% (= 1 mg/ml):||1.083|
The CD40L is a type II membrane protein and is a member of the tumor necrosis factor (TNF) superfamily of proteins. CD40L is transiently expressed on the surface of activated T cells and on the surface of activated platelets. A significant fraction of the surface anchored CD40L heteromultimers consisting of one or two proteolytic TNFH fragments.
The biological significance of these presumed heterotrimers is unclear. Binding of CD40L to its receptor, CD40, which is expressed on the surface of B cells, provides a critical and unique pathway of cellular activation resulting in antibody isotype switching, regulation of apoptosis, B cell proliferation and differentiation. Naturally occurring mutations of CD40L result in the clinical hyper-IgM syndrome, characterized by an inability to produce immunoglobulins of the IgG, IgA and IgE isotypes. The CD40L deficient mice also exhibit a prolonged clotting time, which is consistent with its integrin-binding capacity and its role in clotting cascade.
The extracellular domain of CD40L is made of a ~ 65 aa stalk region and a TNF homologous domain (TNFH). Like other members of the TNF superfamily, CD40L TNFH is responsible for trimerization and for the interaction with its receptor. Soluble trimeric CD40L is produced by proteolytic cleavage of the full-length transmembrane protein and is fully capable of interacting with its receptor, at a 1:3 stoichiometry.
Amino Acid Sequence
1. 2 Å crystal structure of an extracellular fragment of human CD40 ligand. Karpsusas M., Hsu Y.-M., Wang J.-H., Thompson J., Lederman S., Chess L., Thomas D. Structure 3:1031-1039 (1995)
2. Heteromultimeric complexes of CD40 ligand are present on the cell surface of human T lymphocytes. Hsu YM, Lucci J, Su L, Ehrenfels B, Garber E, Thomas D. J Biol Chem. 272: 911-915 (1997)
3. The role of polar interactions in the molecular recognition of CD40L with its receptor CD40. Singh J., Garber E., van Vlijmen H., Karpsusas M., Hsu Y.-M., Zheng Z., Naismith J.H., Thomas D. Protein Sci. 7:1124-1135 (1998)