Structure of a 1.5-MDa adhesin that binds its antarctic bacterium to diatoms and ice
Bacterial adhesins are modular cell-surface proteins that mediate adherence to other cells, surfaces, and ligands. The Antarctic bacterium Marinomonas primoryensis uses a 1.5-MDa adhesin comprising over 130 domains to position it on ice at the top of the water column for better access to oxygen and...
Published in: | Science Advances |
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Main Authors: | , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2017
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Subjects: | |
Online Access: | https://research.tue.nl/en/publications/a68617e0-427b-4438-8eb2-4e9272c91de8 https://doi.org/10.1126/sciadv.1701440 https://pure.tue.nl/ws/files/91221056/guostruc2017.pdf |
Summary: | Bacterial adhesins are modular cell-surface proteins that mediate adherence to other cells, surfaces, and ligands. The Antarctic bacterium Marinomonas primoryensis uses a 1.5-MDa adhesin comprising over 130 domains to position it on ice at the top of the water column for better access to oxygen and nutrients. We have reconstructed this 0.6-μm-long adhesin using a “dissect and build” structural biology approach and have established complementary roles for its five distinct regions. Domains in region I (RI) tether the adhesin to the type I secretion machinery in the periplasm of the bacterium and pass it through the outer membrane. RII comprises ~120 identical immunoglobulin-like β-sandwich domains that rigidify on binding Ca2+ to project the adhesion regions RIII and RIV into the medium. RIII contains ligand-binding domains that join diatoms and bacteria together in a mixed-species community on the underside of sea ice where incident light is maximal. RIV is the ice-binding domain, and the terminal RV domain contains several “repeats-in-toxin” motifs and a noncleavable signal sequence that target proteins for export via the type I secretion system. Similar structural architecture is present in the adhesins of many pathogenic bacteria and provides a guide to finding and blocking binding domains to weaken infectivity. |
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