Structure of a 1.5-MDa adhesin that binds its Antarctic bacterium to diatoms and ice

• DOI: 10.1126/sciadv.1701440
• Publication Date: 2017-08-10T01:20:23Z
• Authors: Shuaiqi Guo; Corey A. Stevens; Tyler D. R. Vance; Luuk L. C. Olijve; Laurie A. Graham; Robert L. Campbell; Saeed R. Yazdi; Carlos Escobedo; Maya Bar-Dolev; Victor Yashunsky; Ido Braslavsky; David N. Langelaan; Steven P. Smith; John S. Allingham; Ilja K. Voets; Peter L. Davies
• Keywords: Models, Molecular; 0301 basic medicine; Ice Cover/microbiology; Protein Conformation; Antarctic Regions; Ligands; Models, Biological; Structure-Activity Relationship; 03 medical and health sciences; Models; Bacterial/chemistry; Ice Cover; Protein Interaction Domains and Motifs; Amino Acid Sequence; 14. Life underwater; Adhesins, Bacterial; Symbiosis; Research Articles; Diatoms; 0303 health sciences; Binding Sites; Type I Secretion Systems; Bacteria; Molecular; Biological; Adhesins; Diatoms/microbiology; Bacteria/metabolism; Biofilms; Type I Secretion Systems/genetics

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 position it on ice at the top of water column for better access oxygen nutrients. We have reconstructed this 0.6-μm-long using "dissect build" structural biology approach established complementary roles its five distinct regions. Domains in region I (RI) tether type secretion machinery periplasm pass through outer membrane. RII comprises ~120 identical immunoglobulin-like β-sandwich rigidify binding Ca2+ project adhesion regions RIII RIV into medium. contains ligand-binding join diatoms bacteria together mixed-species community underside sea where incident light is maximal. ice-binding domain, terminal RV domain several "repeats-in-toxin" motifs noncleavable signal sequence target export via system. Similar architecture present many pathogenic provides guide finding blocking weaken infectivity.