RCSB PDB - 1ALY: CRYSTAL STRUCTURE OF HUMAN CD40 LIGAND (original) (raw)
2 A crystal structure of an extracellular fragment of human CD40 ligand.
[Karpusas, M.](/search?q=citation.rcsb%5Fauthors:Karpusas, M.), [Hsu, Y.M.](/search?q=citation.rcsb%5Fauthors:Hsu, Y.M.), [Wang, J.H.](/search?q=citation.rcsb%5Fauthors:Wang, J.H.), [Thompson, J.](/search?q=citation.rcsb%5Fauthors:Thompson, J.), [Lederman, S.](/search?q=citation.rcsb%5Fauthors:Lederman, S.), [Chess, L.](/search?q=citation.rcsb%5Fauthors:Chess, L.), [Thomas, D.](/search?q=citation.rcsb%5Fauthors:Thomas, D.)
(1995) Structure 3: 1031-1039
PubMed: 8589998 Search on PubMed
PubMed Abstract:
The CD40 ligand (CD40L) is a member of the tumor necrosis factor (TNF) family of proteins and is transiently expressed on the surface of activated T cells. The binding of CD40L to 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, and 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. We have determined the crystal structure of a soluble extracellular fragment of human CD40L to 2 A resolution and with an R factor of 21.8%. Although the molecule forms a trimer similar to that found for other members of the TNF family, such as TNF alpha and lymphotoxin-alpha, and exhibits a similar overall fold, there are considerable differences in several loops including those predicted to be involved in CD40 binding. The structure suggests that most of the hyper-IgM syndrome mutations affect the folding and stability of the molecule rather than the CD40-binding site directly. Despite the fact that the hyper-IgM syndrome mutations are dispersed in the primary sequence, a large fraction of them are clustered in space in the vicinity of a surface loop, close to the predicted CD40-binding site.
Organizational Affiliation:
Biogen, Inc., Cambridge, MA 02142, USA.