Comprehensive analysis of blood group antigen binding to classical and El Tor cholera toxin B-pentamers by NMR.
Cholera is a diarrheal disease responsible for the deaths of thousands, possibly even hundreds of thousands of people every year, and its impact is predicted to further increase with climate change. It has been known for decades that blood group O individuals suffer more severe symptoms of cholera compared with individuals with other blood groups (A, B and AB). The observed blood group dependence is likely to be caused by the major virulence factor of Vibrio cholerae, the cholera toxin (CT). Here, we investigate the binding of ABH blood group determinants to both classical and El Tor CTB-pentamers using saturation transfer difference NMR and show that all three blood group determinants bind to both toxin variants. Although the details of the interactions differ, we see no large differences between the two toxin genotypes and observe very similar binding constants. We also show that the blood group determinants bind to a site distinct from that of the primary receptor, GM1. Transferred NOESY data confirm that the conformations of the blood group determinants in complex with both toxin variants are similar to those of reported X-ray and solution structures. Taken together, this detailed analysis provides a framework for the interpretation of the epidemiological data linking the severity of cholera infection and an individual's blood group, and brings us one step closer to understanding the molecular basis of cholera blood group dependence.
Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
Francesca
F
Vasile
Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
José J
JJ
Reina
Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy.
Donatella
D
Potenza
Department of Chemistry, University of Oslo, PO Box 1033, Blindern NO-0315, Norway.
Julie E
JE
Heggelund
Department of Chemistry, University of Oslo, PO Box 1033, Blindern NO-0315, Norway.
Alasdair
A
Mackenzie
Department of Chemistry, University of Oslo, PO Box 1033, Blindern NO-0315, Norway anna.bernardi@unimi.it ute.krengel@kjemi.uio.no.
Ute
U
Krengel
Dipartimento di Chimica, Universita' degli Studi di Milano, via Golgi 19, 20133 Milano, Italy anna.bernardi@unimi.it ute.krengel@kjemi.uio.no.
Anna
A
Bernardi
D001665:Binding Sites; D001789:Blood Group Antigens / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*; D002236:Carbohydrate Conformation; D002772:Cholera Toxin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data
D001789:Blood Group Antigens; D002772:Cholera Toxin
ABH blood group determinants; binding affinity; cholera blood group dependence; cholera toxin; nuclear magnetic resonance spectroscopy (STD and tr-NOESY)