A Toxoplasma gondii oxopurine transporter binds nucleobases and nucleosides using different binding modes

Campagnaro, G. D., Elati, H. A. A. , Balaska, S., Martin Abril, M. E., Natto, M. J., Hulpia, F., Lee, K., Sheiner, L. , Van Calenbergh, S. and De Koning, H. P. (2022) A Toxoplasma gondii oxopurine transporter binds nucleobases and nucleosides using different binding modes. International Journal of Molecular Sciences, 23(2), 710. (doi: 10.3390/ijms23020710) (PMID:35054895) (PMCID:PMC8776092)

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Toxoplasma gondii is unable to synthesize purines de novo, instead salvages them from its environment, inside the host cell, for which they need high affinity carriers. Here, we report the expression of a T. gondii Equilibrative Nucleoside Transporter, Tg244440, in a Trypanosoma brucei strain from which nucleobase transporters have been deleted. Tg244440 transported hypoxanthine and guanine with similar affinity (Km ~1 µM), while inosine and guanosine displayed Ki values of 4.05 and 3.30 µM, respectively. Low affinity was observed for adenosine, adenine, and pyrimidines, classifying Tg244440 as a high affinity oxopurine transporter. Purine analogues were used to probe the substrate-transporter binding interactions, culminating in quantitative models showing different binding modes for oxopurine bases, oxopurine nucleosides, and adenosine. Hypoxanthine and guanine interacted through protonated N1 and N9, and through unprotonated N3 and N7 of the purine ring, whereas inosine and guanosine mostly employed the ribose hydroxy groups for binding, in addition to N1H of the nucleobase. Conversely, the ribose moiety of adenosine barely made any contribution to binding. Tg244440 is the first gene identified to encode a high affinity oxopurine transporter in T. gondii and, to the best of our knowledge, the first purine transporter to employ different binding modes for nucleosides and nucleobases.

Item Type:Articles
Additional Information:This research was funded by ScienceWithout Borders, grant number 206385/2014-5, CNPq, Brazil (scholarship to GDC); the Libyan government (scholarship to HAAE); the European Union (Erasmus+ for SB); the International Association for the Exchange of Students for Technical Experience provided a bursary to MEMA; M.J.N. was funded through a Fellowship from the Saudi Arabian Ministry of Health; F.H. was supported by the Flanders Research Foundation FWO (grant number 1226921 N) and L.S. by a grant from the Medical Research Council, UK, grant number MR/S024573/1.
Glasgow Author(s) Enlighten ID:Campagnaro, Gustavo and De Koning, Professor Harry and Elati, Hamza Ali Abd and Natto, Dr Manal and Sheiner, Dr Lilach
Creator Roles:
Campagnaro, G.Methodology, Formal analysis, Investigation, Writing – original draft, Funding acquisition
Elati, H. A. A.Investigation
Natto, M.Methodology
Sheiner, L.Writing – review and editing, Supervision
De Koning, H.Conceptualization, Formal analysis, Data curation, Writing – original draft, Supervision, Funding acquisition
Authors: Campagnaro, G. D., Elati, H. A. A., Balaska, S., Martin Abril, M. E., Natto, M. J., Hulpia, F., Lee, K., Sheiner, L., Van Calenbergh, S., and De Koning, H. P.
College/School:College of Medical Veterinary and Life Sciences
College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:International Journal of Molecular Sciences
ISSN (Online):1422-0067
Copyright Holders:Copyright © 2022 The Authors
First Published:International Journal of Molecular Sciences 23(2):710
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
305129How do REDox regulators control Apicoplast functions in the parasites causing TOxoplasmosis and MalariaLilach SheinerMedical Research Council (MRC)MR/S024573/1III - Parasitology