Send to

Choose Destination
Proc Natl Acad Sci U S A. 2016 Sep 20;113(38):10542-6. doi: 10.1073/pnas.1612603113. Epub 2016 Sep 6.

Structure of Bor1 supports an elevator transport mechanism for SLC4 anion exchangers.

Author information

Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158.
Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158


Boron is essential for plant growth because of its incorporation into plant cell walls; however, in excess it is toxic to plants. Boron transport and homeostasis in plants is regulated in part by the borate efflux transporter Bor1, a member of the solute carrier (SLC) 4 transporter family with homology to the human bicarbonate transporter Band 3. Here, we present the 4.1-Å resolution crystal structure of Arabidopsis thaliana Bor1. The structure displays a dimeric architecture in which dimerization is mediated by centralized Gate domains. Comparisons with a structure of Band 3 in an outward-open state reveal that the Core domains of Bor1 have rotated inwards to achieve an occluded state. Further structural comparisons with UapA, a xanthine transporter from the nucleobase-ascorbate transporter family, show that the downward pivoting of the Core domains relative to the Gate domains may access an inward-open state. These results suggest that the SLC4, SLC26, and nucleobase-ascorbate transporter families all share an elevator transport mechanism in which alternating access is provided by Core domains that carry substrates across a membrane.


Band 3; Bor1; SLC4 transporter; X-ray structure; membrane protein

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center