3LDJ: Crystal Structure Of Aprotinin In Complex With Sucrose Octasulfate: Unusual Interactions And Implication For Heparin Binding

The crystal structures of aprotinin and its complex with sucrose octasulfate (SOS), a polysulfated heparin analog, were determined at 1.7-2.6A resolutions. Aprotinin is monomeric in solution, which associates into a decamer at high salt concentrations. Sulfate ions serve to neutralize the basic amino acid residues of aprotinin to stabilize the decameric aprotinin. Whereas SOS interacts with heparin binding proteins at 1:1 molar ratio, SOS was surprisingly found to induce strong agglutination of aprotinins. Five molecules of aprotinin interact with one molecule of the sulfated sugar, which is stabilized by electrostatic interactions between the positively charged residues of aprotinin and sulfate groups of SOS. The multiple binding modes of SOS with five individual aprotinin molecules may represent the diverse patterns of potential heparin binding to aprotinin, reflecting the interactions of densely packed protein molecules along the heparin polymer.
PDB ID: 3LDJDownload
MMDB ID: 84804
PDB Deposition Date: 2010/1/13
Updated in MMDB: 2010/09
Experimental Method:
x-ray diffraction
Resolution: 1.7  Å
Source Organism:
Similar Structures:
Biological Unit for 3LDJ: monomeric; determined by author and by software (PISA)
Molecular Components in 3LDJ
Label Count Molecule
Protein (1 molecule)
Pancreatic Trypsin Inhibitor(Gene symbol: PTI)
Molecule annotation
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Citing MMDB