Structural analyses of carbohydrate receptors for enterotoxins and adhesins of enterotoxigenic Escherichia coli
Abstract
Carbohydrate-binding proteins expressed by microbes are key determinants in initiating
and sustaining infections that account for millions of deaths each year. This thesis fo-
cused on proteins integral to infections instigated by enterotoxigenic Escherichia coli
(ETEC); estimated as the largest bacterial cause of diarrhea in the world with hundreds
of millions of cases each year. ETEC infections are mediated by two primary carbohy-
drate-binding proteins; 1) Colonization factors (CF), which facilitate host cell attach-
ment, and 2) Enterotoxins, which penetrate host cells to induce a potentially lethal diar-
rheal response. By employing biochemical techniques, such as chromatogram binding
assays, mass spectrometry and NMR, we dissected the precise mechanisms fundamental
for the interactions of ETEC carbohydrate-binding proteins.
In the presented papers, the novel colonization factor CS30, and the enterotoxins LT-
IIb, and LT-IIc where investigated. Our findings identified the sulfatide glycosphin-
golipid as the principal receptor for CS30 and emphasized the significance of the car-
bohydrate-presenting lipid moiety in binding. The diarrhea-inducing toxins, LT-IIb and
LT-IIc, demonstrated distinct binding specificity to sialic acid presenting glycosphin-
golipids, and the presence of such receptors were confirmed in the human intestine.
Lastly, structural studies detailed the atomic framework of these binding interactions
and quantified the binding affinities.
By revealing the specific carbohydrate interactions underpinning both adhesion and
toxin action, our study uncovers the intricate processes governing pathogenic infection
mechanisms, which may inform the design of next-generation anti-bacterial therapeu-
tics, vaccines and diagnostical tools.
Parts of work
Zalem D, Ribeiro JP, Varrot A, Lebens M, Imberty A, Teneberg S. Biochem-
ical and structural characterization of the novel sialic acid-binding site of Esch-
erichia coli heat-labile enterotoxin LT-IIb. Biochemical Journal. 2016 Nov
1;473(21):3923-3936. https://doi.org/10.1042/bcj20160575 Von Mentzer A, Zalem D, Chrienova Z, Teneberg S. Colonization factor CS30
from enterotoxigenic Escherichia coli binds to sulfatide in human and porcine
small intestine. Virulence. 2020 Dec;11(1):381-390. https://doi.org/10.1080/21505594.2020.1749497 Zalem D, Juhás M, Terrinoni M, King-Lyons N, Lebens M, Varrot A, Connell
TD, Teneberg S. Characterization of the ganglioside recognition profile of
Escherichia coli heat-labile enterotoxin LT-IIc. Glycobiology. 2022 Apr
21;32(5):391-403. https://doi.org/10.1093/glycob/cwab133 Zalem D, Lebens M, Teneberg S, Karlsson G. Structural and
dynamic studies of Escherichia coli heat-labile enterotoxin
LT-IIb B-subunits by NMR spectroscopy. Manuscript.
Degree
Doctor of Philosophy (Medicine)
University
University of Gothenburg. Sahlgrenska Academy
Institution
Institute of Biomedicine. Department of Medical Biochemistry and Cell Biology
Disputation
Fredagen den 1 december 2023, kl. 13.00, Hörsal Arvid Carlsson, Academicum, Medicinaregatan 3, Göteborg
Date of defence
2023-12-01
dani.zalem@gu.se
Date
2023-11-10Author
Zalem, Dani
Keywords
Carbohydrate recognition
glycosphingolipid
diarrheagenic E. coli
ETEC
heat-labile enterotoxin
colonization factor
AB5 toxins
Publication type
Doctoral thesis
ISBN
978-91-8069-533-6 (tryck)
978-91-8069-534-3 (pdf)
Language
eng