Use of Atomic Force Microscopy to Study the Multi-Modular Interaction of Bacterial Adhesins to Mucins.
The mucus layer covering the gastrointestinal (GI) epithelium is critical in selecting and maintaining homeostatic interactions with our gut bacteria. However, the molecular details of these interactions are not well understood. Here, we provide mechanistic insights into the adhesion properties of the canonical mucus-binding protein (MUB), a large multi-repeat cell-surface adhesin found inLactobacillusinhabiting the GI tract. We used atomic force microscopy to unravel the mechanism driving MUB-mediated adhesion to mucins. Using single-molecule force spectroscopy we showed that MUB displayed remarkable adhesive properties favouring a nanospring-like adhesion model between MUB and mucin mediated by unfolding of the multiple repeats constituting the adhesin. We obtained direct evidence for MUB self-interaction; MUB-MUB followed a similar binding pattern, confirming that MUB modular structure mediated such mechanism. This was in marked contrast with the mucin adhesion behaviour presented by Galectin-3 (Gal-3), a mammalian lectin characterised by a single carbohydrate binding domain (CRD). The binding mechanisms reported here perfectly match the particular structural organization of MUB, which maximizes interactions with the mucin glycan receptors through its long and linear multi-repeat structure, potentiating the retention of bacteria within the outer mucus layer.
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. patrick.gunning@ifr.ac.uk.
A Patrick
AP
Gunning
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Devon.Kavanaugh@ifr.ac.uk.
Devon
D
Kavanaugh
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Elizabeth.Thursby@ifr.ac.uk.
Elizabeth
E
Thursby
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. sabrinaetzold1@gmail.com.|Division of Neonatology and Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, School of Medicine, University of California San Diego, 9500 Gilman Drive, San Diego, CA 92093-0715, USA. sabrinaetzold1@gmail.com.
Sabrina
S
Etzold
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. d.mackenzie91@btinternet.com.
Donald A
DA
MacKenzie
The Gut Health and Food Safety Institute Strategic Programme, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. nathalie.juge@ifr.ac.uk.
Nathalie
N
Juge
D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D001422:Bacterial Adhesion; D017077:Culture Media, Conditioned / Q000737:chemistry; D037502:Galectin 3 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry; D052200:Limosilactobacillus reuteri / Q000254:growth & development / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D055263:Mucin-3 / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013552:Swine
D018829:Adhesins, Bacterial; D017077:Culture Media, Conditioned; D037502:Galectin 3; D055263:Mucin-3; D011994:Recombinant Proteins
Lactobacillus reuteri; atomic force microscopy; bacterial adhesins; gut microbiota; intestinal mucin; mucus binding protein; single molecule force spectroscopy