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The structures of crystalline complexes of human serum amyloid P component with its carbohydrate ligand, the cyclic pyruvate acetal of galactose.
journal contributionposted on 2023-06-08, 06:07 authored by D Thompson, M B Pepys, I Tickle, S Wood
wo monoclinic (P21) crystal forms of human serum amyloid P component (SAP) in complex with the 4,6-pyruvate acetal of ß- -galactose (MOßDG) were prepared. Structure analysis by molecular replacement and refinement at 2.2 Å resolution revealed that crystal form 1 (a=95.76 Å, b=70.53 Å, c=103.41 Å, ß=96.80°) contained a pentamer in the asymmetric unit with a structure very similar to that of the published search model. The mode of ligand co-ordination was also similar except that four of the five subunits showed bound ligand with an additional H-bond between O1 of the galactose and the side-chain of Lys79. One sub-unit showed no bound ligand and a vacant calcium site close to a crystal contact. The 2.6 Å resolution structure of crystal form 2 (a=118.60 Å, b=109.10 Å, c=120.80 Å and ß=95.16°) showed ten sub-units in the asymmetric unit, all with two bound calcium ions and ligand. The most extensive protein¿protein interactions between pentamers describe an AB face-to-face interaction involving 15 ion pairs that sandwiches five molecules of bound MOßDG at the interface.
JournalJournal of Molecular Biology
Department affiliated with
- Biochemistry Publications
NotesAll Thompson's work. This is the first structure of this protein complexed with a natural ligand.
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