PT  - JOURNAL ARTICLE
AU  - Michael J. Capper
AU  - Shifan Yang
AU  - Alexander C. Stone
AU  - Sezen Vatansever
AU  - Gregory Zilberg
AU  - Yamuna Kalyani Mathiharan
AU  - Raul Habib
AU  - Keino Hutchinson
AU  - Avner Schlessinger
AU  - Mihaly Mezei
AU  - Roman Osman
AU  - Bin Zhang
AU  - Daniel Wacker
TI  - Substrate Binding and Inhibition of the Anion Exchanger 1 Transporter
AID  - 10.1101/2022.02.11.480130
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.02.11.480130
4099  - http://biorxiv.org/content/early/2022/02/12/2022.02.11.480130.short
4100  - http://biorxiv.org/content/early/2022/02/12/2022.02.11.480130.full
AB  - Anion Exchanger 1 (AE1, SLC4A1) is the primary bicarbonate (HCO3-) transporter expressed in erythrocyte membranes where it mediates transport of CO2 between lungs and other tissues via import/export of bicarbonate. It is also a key regulator of erythrocyte structure and antigenic recognition. Previous biochemical studies, and a low-resolution crystal structure of the transmembrane domain have provided initial insight into AE1 structure and function. However, key questions remain regarding substrate binding and transport as well as the mechanism of inhibition. The orientation of the intracellular domain as well as the localization of lipid and sterol binding sites also remain enigmatic. We herein present seven novel high resolution cryo-EM structures of the full length human transporter in the apo, bicarbonate-bound, and several inhibitor-bound states combined with uptake- and computational studies. To our knowledge, these studies represent the first full length human, and substrate bound, SLC4 transporter structure. Our results reveal important molecular details about substrate binding and transport, as well as the diverse mechanisms of AE1 inhibition by both research chemicals and prescription drugs. We also provide novel insights into the full-length transporter architecture, identify the conformational space of the Diego blood antigen system and elucidate multiple lipid and sterol binding sites.Competing Interest StatementThe authors have declared no competing interest.