Structural basis for the role of serine-rich repeat proteins fromLactobacillus reuteriin gut microbe-host interactions.

Sequeira S., Kavanaugh D., MacKenzie D. A., Suligoj T., Walpole S., Leclaire C., Gunning A. P., Latousakis D., Willats W. G. T., Angulo J., Dong C., Juge N.. (2018)

Proceedings of the National Academy of Sciences of the United States of America

Lactobacillus reuteri , a Gram-positive bacterial species inhabiting the gastrointestinal tract of vertebrates, displays remarkable host adaptation. Previous mutational analyses of rodent strainL. reuteri100-23C identified a gene encoding a predicted surface-exposed serine-rich repeat protein (SRRP100-23) that was vital forL. reuteribiofilm formation in mice. SRRPs have emerged as an important group of surface proteins on many pathogens, but no structural information is available in commensal bacteria. Here we report the 2.00-Å and 1.92-Å crystal structures of the binding regions (BRs) of SRRP100-23and SRRP53608fromL. reuteriATCC 53608, revealing a unique ß-solenoid fold in this important adhesin family. SRRP53608-BR bound to host epithelial cells and DNA at neutral pH and recognized polygalacturonic acid (PGA), rhamnogalacturonan I, or chondroitin sulfate A at acidic pH. Mutagenesis confirmed the role of the BR putative binding site in the interaction of SRRP53608-BR with PGA. Long molecular dynamics simulations showed that SRRP53608-BR undergoes a pH-dependent conformational change. Together, these findings provide mechanistic insights into the role of SRRPs in host-microbe interactions and open avenues of research into the use of biofilm-forming probiotics against clinically important pathogens.

Proceedings of the National Academy of Sciences of the United States of America

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