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Resculpting the binding pocket of APC superfamily LeuT-fold amino acid transporters

Lookup NU author(s): Dr Noel Edwards, Dr Catriona Anderson, Nichola Conlon, Andrew Watson, Dr Timothy Cheek, Professor T. Martin Embley, Professor David Thwaites

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

© 2017 The Author(s) Amino acid transporters are essential components of prokaryote and eukaryote cells, possess distinct physiological functions, and differ markedly in substrate specificity. Amino acid transporters can be both drug targets and drug transporters (bioavailability, targeting) with many monogenic disorders resulting from dysfunctional membrane transport. The largest collection of amino acid transporters (including the mammalian SLC6, SLC7, SLC32, SLC36, and SLC38 families), across all kingdoms of life, is within the Amino acid-Polyamine-organoCation (APC) superfamily. The LeuT-fold is a paradigm structure for APC superfamily amino acid transporters and carriers of sugars, neurotransmitters, electrolytes, osmolytes, vitamins, micronutrients, signalling molecules, and organic and fatty acids. Each transporter is specific for a unique sub-set of solutes, specificity being determined by how well a substrate fits into each binding pocket. However, the molecular basis of substrate selectivity remains, by and large, elusive. Using an integrated computational and experimental approach, we demonstrate that a single position within the LeuT-fold can play a crucial role in determining substrate specificity in mammalian and arthropod amino acid transporters within the APC superfamily. Systematic mutation of the amino acid residue occupying the equivalent position to LeuT V104 titrates binding pocket space resulting in dramatic changes in substrate selectivity in exemplar APC amino acid transporters including PAT2 (SLC36A2) and SNAT5 (SLC38A5). Our work demonstrates how a single residue/site within an archetypal structural motif can alter substrate affinity and selectivity within this important superfamily of diverse membrane transporters.


Publication metadata

Author(s): Edwards N, Anderson CMH, Conlon NJ, Watson AK, Hall RJ, Cheek TR, Embley TM, Thwaites DT

Publication type: Article

Publication status: Published

Journal: Cellular and Molecular Life Sciences

Year: 2018

Volume: 75

Issue: 5

Pages: 921-938

Print publication date: 01/03/2018

Online publication date: 23/10/2017

Acceptance date: 02/10/2017

ISSN (print): 1420-682X

ISSN (electronic): 1420-9071

Publisher: Birkhauser Verlag AG

URL: https://doi.org/10.1007/s00018-017-2677-8

DOI: 10.1007/s00018-017-2677-8


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