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Figure 2.
Figure 2. Crystal Structures of the IgSF Domain of CD47
(A) The secondary structure of CD47 is shown above the sequence
of the IgSF domain of human CD47 with arrows and cylinders
representing β sheets and α helices, respectively. The
N-terminal glutamine residue that cyclizes to form a
pyroglutamate is boxed. The cysteine residues that form a
conserved disulphide bond between β sheets are highlighted in
yellow. C15, which forms a disulphide link with the 5
transmembrane helix C-terminal domain of CD47, is starred.
Residues where N-linked glycosylation was observed in at least
one monomer of CD47 are colored magenta.
(B) CD47 (shown as
ribbons) crystallized as a dimer where the G strands are swapped
between pairs of molecules. The structure is color ramped from
blue (N terminus) to red (C terminus), and the strands are
labeled A–G. The three insets show the N-terminal
pyroglutamate, the region between the domains together with the
Mg^2+ that is assumed to facilitate the strand-swap, and one of
the sites of N-linked glycosylation. In all insets, the final
refined model is shown in 2F[O]-F[C] electron density (1.3 σ)
calculated at the end of refinement.
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