Structures of the Streptococcus sanguinis SrpA Binding Region with Human Sialoglycans Suggest Features of the Physiological Ligand
- Vanderbilt Univ., Nashville, TN (United States)
- Univ. of California, San Francisco, CA (United States); Northern California Institute for Research and Education, San Francisco, CA (United States)
- Univ. of California, Davis, CA (United States)
- Univ. of California, Davis, CA (United States); Henan Inst. of Science and Technology, Xinxiang (China)
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 (SrpABR) with five low-affinity ligands: three sialylated trisaccharides (sialyl-T antigen, 3'-sialyllactose, and 3'-sialyl-N-acetyllactosamine), a sialylated tetrasaccharide (sialyl-LewisX), 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 SrpABR and glycans are important for binding to platelets and to better map the binding site for the physiological receptor. Here, we found that the sialoglycan binding site of SrpABR 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.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; National Inst. of Health; Michigan Economic Development Corp.; Michigan Technology Tri-Corridor; American Heart Association
- Grant/Contract Number:
- AC02-06CH11357; S10 RR026915; 085P1000817; AI41513; AI106987; 14GRNT20390021
- OSTI ID:
- 1331707
- Journal Information:
- Biochemistry, Vol. 55, Issue 42; ISSN 0006-2960
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- ENGLISH
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