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Figure 2.
Fig. 2. Interactions of individual SpA domains. (A)
Alignment of the amino acid sequences of the five SpA domains.
Domain D residues involved in interaction with Fab 2A2 are
highlighted in cyan. With the exception of Gln-32 (pink), there
is no overlap between the residues involved in Fab interaction
and those mediating Fc  binding (2)
(gray highlight). The engineered domain Z differs by the key
mutation Gly-29 in Ala and does not bind Fab. The residues
involved in the dimer of domain D observed in the asymmetric
unit are indicated by red and green boxes. (B) Cross-linking of
a V[H]3 Fab (cyan surface) and a Fc (gray
surface) by a single domain of SpA (red ribbon). This model is
based on the superposition of helix I and II of SpA domains in
the Fab-domain D complex reported here and in the previously
determined Fc -domain B
complex (2) (rmsd of 0.73 Å for 140 backbone atoms). (C)
Interface between domain D monomers. Schematic view of the
interaction between the two domains D observed in the asymmetric
unit, dom-D1 (red ribbon) and dom-D2 (green ribbon). Contact
residues from both domains are shown in stick representation.
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