6VS7

Sialic acid binding region of Streptococcus Sanguinis SK1 adhesin

Summary for 6VS7

• Entry DOI: 10.2210/pdb6vs7/pdb
• Descriptor: Adhesin, CALCIUM ION, SULFATE ION, ... (8 entities in total)
• Functional Keywords: bacterial adhesion, adhesin, serine rich repeat, streptococcus, cell adhesion
• Biological source: Streptococcus sanguinis SK1 = NCTC 7863
• Total number of polymer chains: 2
• Total formula weight: 90625.84

Authors

Stubbs, H.E.,Iverson, T.M. (deposition date: 2020-02-10, release date: 2020-08-26, Last modification date: 2023-10-11)

Primary citation

Stubbs, H.E.,Bensing, B.A.,Yamakawa, I.,Sharma, P.,Yu, H.,Chen, X.,Sullam, P.M.,Iverson, T.M.
Tandem sialoglycan-binding modules in a Streptococcus sanguinis serine-rich repeat adhesin create target dependent avidity effects.
J.Biol.Chem., 295:14737-14749, 2020

PubMed Abstract: ialic acid-binding mmunolobulin-like tins (Siglec)-like domains of streptococcal serine-rich repeat (SRR) adhesins recognize sialylated glycans on human salivary, platelet, and plasma glycoproteins via a YTRY sequence motif. The SRR adhesin from strain SK1 has tandem sialoglycan-binding domains and has previously been shown to bind sialoglycans with high affinity. However, both domains contain substitutions within the canonical YTRY motif, making it unclear how they interact with host receptors. To identify how the strain SK1 SRR adhesin affects interactions with sialylated glycans and glycoproteins, we determined high-resolution crystal structures of the binding domains alone and with purified trisaccharides. These structural studies determined that the ligands still bind at the noncanonical binding motif, but with fewer hydrogen-bonding interactions to the protein than is observed in structures of other Siglec-like adhesins. Complementary biochemical studies identified that each of the two binding domains has a different selectivity profile. Interestingly, the binding of SK1 to platelets and plasma glycoproteins identified that the interaction to some host targets is dominated by the contribution of one binding domain, whereas the binding to other host receptors is mediated by both binding domains. These results provide insight into outstanding questions concerning the roles of tandem domains in targeting host receptors and suggest mechanisms for how pathogens can adapt to the availability of a range of related but nonidentical host receptors. They further suggest that the definition of the YTRY motif should be changed to ϕTR, a more rigorous description of this sialic acid-recognition motif given recent findings.

PubMed: 32820052
DOI: 10.1074/jbc.RA120.014177

Experimental method

X-RAY DIFFRACTION (2 Å)