Complement component C3 plays a key role in the complement-mediated immune defence, and occupies a central position within the complement cascade system. One of its degradation products, C3dg, was purified from rat serum and crystallised in two different crystal forms as N-terminally truncated fragment. Despite the truncation and the lack of a significant portion of the N-terminus as compared to C3d, the structure of the fragment is highly similar to that of recombinant human C3d (Nagar et al., Science 280 (1998) 1277-1281). Structural details of the reactive site have been obtained, suggesting a possible mode of thioester bond formation between Cys-1010 and Gin-1013 and thioester bond cleavage in the transacylation reaction involving His-1126. The truncation at the N-terminus of C3d leads to the exposure of a surface of the molecule that favours dimerisation, so that in both crystal forms, the fragment is present as a dimer, with monomers related by a two-fold axis.

Structure at 1.44 A resolution of a N-terminally truncated form of rat serum complement C3d,g fragment

ZANOTTI, GIUSEPPE;BATTISTUTTA, ROBERTO;
2000

Abstract

Complement component C3 plays a key role in the complement-mediated immune defence, and occupies a central position within the complement cascade system. One of its degradation products, C3dg, was purified from rat serum and crystallised in two different crystal forms as N-terminally truncated fragment. Despite the truncation and the lack of a significant portion of the N-terminus as compared to C3d, the structure of the fragment is highly similar to that of recombinant human C3d (Nagar et al., Science 280 (1998) 1277-1281). Structural details of the reactive site have been obtained, suggesting a possible mode of thioester bond formation between Cys-1010 and Gin-1013 and thioester bond cleavage in the transacylation reaction involving His-1126. The truncation at the N-terminus of C3d leads to the exposure of a surface of the molecule that favours dimerisation, so that in both crystal forms, the fragment is present as a dimer, with monomers related by a two-fold axis.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/113158
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