5IJ2

SrpA adhesin in complex with sialyllactosamine

Summary for 5IJ2

• Entry DOI: 10.2210/pdb5ij2/pdb
• Related: 5IIY 5IJ1 5IJ3
• Related PRD ID: PRD_900067
• Descriptor: Platelet-binding glycoprotein, N-acetyl-alpha-neuraminic acid-(2-3)-beta-D-galactopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: adhesin, sugar binding protein
• Biological source: Streptococcus sanguinis (strain SK36)
• Total number of polymer chains: 2
• Total formula weight: 45341.04

Authors

Iverson, T.M. (deposition date: 2016-03-01, release date: 2017-02-08, Last modification date: 2020-07-29)

Primary citation

Loukachevitch, L.V.,Bensing, B.A.,Yu, H.,Zeng, J.,Chen, X.,Sullam, P.M.,Iverson, T.M.
Structures of the Streptococcus sanguinis SrpA Binding Region with Human Sialoglycans Suggest Features of the Physiological Ligand.
Biochemistry, 2016

PubMed Abstract: Streptococcus sanguinis is a leading cause of bacterial infective endocarditis, a life-threatening infection of heart valves. S. sanguinis binds to human platelets with high avidity, and this adherence is likely to enhance virulence. Previous studies suggest that a serine-rich repeat adhesin termed SrpA mediates the binding of S. sanguinis to human platelets via its interaction with sialoglycans on the receptor GPIbα. However, in vitro binding assays with SrpA and defined sialoglycans failed to identify specific high-affinity ligands. To improve our understanding of the interaction between SrpA and human platelets, we determined cocrystal structures of the SrpA sialoglycan binding region (SrpA) with five low-affinity ligands: three sialylated trisaccharides (sialyl-T antigen, 3'-sialyllactose, and 3'-sialyl-N-acetyllactosamine), a sialylated tetrasaccharide (sialyl-Lewis), and a sialyl galactose disaccharide component common to these sialoglyans. We then combined structural analysis with mutagenesis to further determine whether our observed interactions between SrpA and glycans are important for binding to platelets and to better map the binding site for the physiological receptor. We found that the sialoglycan binding site of SrpA is significantly larger than the sialoglycans cocrystallized in this study, which suggests that binding of SrpA to platelets either is multivalent or occurs via a larger, disialylated glycan.

PubMed: 27685666
DOI: 10.1021/acs.biochem.6b00704

Experimental method

X-RAY DIFFRACTION (1.683 Å)