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The calcium-induced conformation and glycosylation of scavenger-rich cysteine repeat (SRCR) domains of glycoprotein 340 influence the high affinity interaction with antigen I/II homologs.

ABSTRACT: Oral streptococci adhere to tooth-immobilized glycoprotein 340 (GP340) via the surface protein antigen I/II (AgI/II) and its homologs as the first step in pathogenesis. Studying this interaction using recombinant proteins, we observed that calcium increases the conformational stability of the scavenger-rich cysteine repeat (SRCRs) domains of GP340. Our results also show that AgI/II adheres specifically with nanomolar affinity to the calcium-induced SRCR conformation in an immobilized state and not in solution. This interaction is significantly dependent on the O-linked carbohydrates present on the SRCRs. This study also establishes that a single SRCR domain of GP340 contains the two surfaces to which the apical and C-terminal regions of AgI/II noncompetitively adhere. Compared with the single SRCR domain, the three tandem SRCR domains displayed a collective/cooperative increase in their bacterial adherence and aggregation. The previously described SRCRP2 peptide that was shown to aggregate several oral streptococci displayed limited aggregation and also nonspecific adherence compared to SRCR domains. Finally, we show distinct species-specific adherence/aggregation between Streptococcus mutans AgI/II and Streptococcus gordonii SspB in their interaction with the SRCRs. This study concludes that identification of the metal ion and carbohydrate adherence motifs on both SRCRs and AgI/II homologs could lead to the development of anti-adhesive inhibitors that could deter the adherence of pathogenic oral streptococci and thereby prevent the onset of infections.

SUBMITTER: Purushotham S

PROVIDER: S-EPMC4139206 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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The calcium-induced conformation and glycosylation of scavenger-rich cysteine repeat (SRCR) domains of glycoprotein 340 influence the high affinity interaction with antigen I/II homologs.

Purushotham Sangeetha S Deivanayagam Champion C

The Journal of biological chemistry 20140612 32

Oral streptococci adhere to tooth-immobilized glycoprotein 340 (GP340) via the surface protein antigen I/II (AgI/II) and its homologs as the first step in pathogenesis. Studying this interaction using recombinant proteins, we observed that calcium increases the conformational stability of the scavenger-rich cysteine repeat (SRCRs) domains of GP340. Our results also show that AgI/II adheres specifically with nanomolar affinity to the calcium-induced SRCR conformation in an immobilized state and n ...[more]

PMID: 24923446

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Project description:The scavenger receptor cysteine-rich (SRCR) family comprises a group of membrane-attached or secreted proteins that contain one or more modules/domains structurally similar to the membrane distal domain of type I macrophage scavenger receptor. Although no all-inclusive biological function has been ascribed to the SRCR family, some of these receptors have been shown to recognize pathogen-associated molecular patterns (PAMP) of bacteria, fungi, or other microbes. SSc5D is a recently described soluble SRCR receptor produced by monocytes/macrophages and T lymphocytes, consisting of an N-terminal portion, which contains five SRCR modules, and a large C-terminal mucin-like domain. Toward establishing a global common role for SRCR domains, we interrogated whether the set of five SRCR domains of SSc5D displayed pattern recognition receptor (PRR) properties. For that purpose, we have expressed in a mammalian expression system the N-terminal SRCR-containing moiety of SSc5D (N-SSc5D), thus excluding the mucin-like domain likely by nature to bind microorganisms, and tested the capacity of the SRCR functional groups to physically interact with bacteria. Using conventional protein-bacteria binding assays, we showed that N-SSc5D had a superior capacity to bind to Escherichia coli strains RS218 and IHE3034 compared with that of the extracellular domains of the SRCR proteins CD5 and CD6 (sCD5 and sCD6, respectively), and similar E. coli-binding properties as Spα, a proven PRR of the SRCR family. We have further designed a more sensitive, real-time, and label-free surface plasmon resonance (SPR)-based assay and examined the capacity of N-SSc5D, Spα, sCD5, and sCD6 to bind to different bacteria. We demonstrated that N-SSc5D compares with Spα in the capacity to bind to E. coli and Listeria monocytogenes, and further that it can distinguish between pathogenic E. coli RS218 and IHE3034 strains and the non-pathogenic laboratory E. coli strain BL21(DE3). Our work thus advocates the utility of SPR-based assays as sensitive tools for the rapid screening of interactions between immune-related receptors and PAMP-bearing microbes. The analysis of our results suggests that SRCR domains of different members of the family have a differential capacity to interact with bacteria, and further that the same receptor can discriminate between different bacteria strains and species.

Dataset Information

The calcium-induced conformation and glycosylation of scavenger-rich cysteine repeat (SRCR) domains of glycoprotein 340 influence the high affinity interaction with antigen I/II homologs.

Publications

The calcium-induced conformation and glycosylation of scavenger-rich cysteine repeat (SRCR) domains of glycoprotein 340 influence the high affinity interaction with antigen I/II homologs.

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