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Published on: September 10, 2020
Structural studies and functional engineering of NanX: an anhydro-sialic acid transporter from Escherichia coli
Michael C Newton-Vesty1,2, Kelsi R Hall1, Zachary D Tillett1
1Biomolecular Interaction Centre, School of Biological Sciences, MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, New Zealand.
Abstract:
NanT and NanX are bacterial transporters that import the sialic acids, N-acetylneuraminate and 2,7-anhydro-n-acetylneuraminate, respectively. Here, we used complementary biophysical and computational approaches to structurally characterise Escherichia coli NanX. Size exclusion chromatography, analytical ultracentrifugation and low-resolution cryo-electron microscopy reveal that NanX exists in both monomeric and dimeric states following purification. Molecular modelling and substrate docking identify key residues likely involved in 2,7-anhydro-n-acetylneuraminate recognition. Using this information, we engineered a mutant NanX transporter that can import the NanT-specific substrate, N-acetylneuraminate, which we verified using a bacterial growth assay. These data identify amino acids involved in major facilitator superfamily mediated sialic acid transport and offer a new research perspective of its metabolism.
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