Structure and function of an Arabidopsis thaliana sulfate transporter

Abstract

Plant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO42−) and are essential for plant growth; however, our understanding of their structures and functions remains inadequate. Here we present the structure of a SULTR from Arabidopsis thaliana, AtSULTR4;1, in complex with SO42− at an overall resolution of 2.8 Å. AtSULTR4;1 forms a homodimer and has a structural fold typical of the SLC26 family of anion transporters. The bound SO42− is coordinated by side-chain hydroxyls and backbone amides, and further stabilized electrostatically by the conserved Arg393 and two helix dipoles. Proton and SO42− are co-transported by AtSULTR4;1 and a proton gradient significantly enhances SO42− transport. Glu347, which is ~7 Å from the bound SO42−, is required for H+-driven transport. The cytosolic STAS domain interacts with transmembrane domains, and deletion of the STAS domain or mutations to the interface compromises dimer formation and reduces SO42− transport, suggesting a regulatory function of the STAS domain.

Lipid-membrane protein interaction visualised by cryo-EM: A review

“…Another member of SLC26 family is the Sulfate Transporter SULTR from Arabidopsis thaliana. Its SO4 2bound structure in GDN (PDB ID: 7LHV) [47] also shows a bilayer-like shape, although it is not as clear as the other structures (not illustrated).…”

MicroRNA Mediated Plant Responses to Nutrient Stress

“…Low-affinity S carriers, such as SULTR2;1, SULTR2;2, and SULTR3;5, are used in plants during S transfer [ 80 ]. Sulfate acclimatization occurs via plasmidic ATP sulfurylase (APS), which can be deposited in vesicles or absorbed in chloroplasts [ 81 ].…”

Role of SLC4 and SLC26 solute carriers during oxidative stress

“…The structure of mammalian SLC26 transporters has long been elusive. Structures of the murine Slc26a9, 118 two bacterial homologues—a bicarbonate transporter from cyanobacteria (BicA) 119 and a proton‐coupled fumarate transporter from the bacterium Deinococcus geothermalis (SLC26Dg), 120 and a plant homologue of SLC26—the vacuolar H + /SO 4 2 symporter SULTR4;1 from Arabidopsis thaliana 121 were solved recently by X‐ray crystallography and cryo‐electron microscopy. These structures show a shared architecture consisting of 14 transmembrane α‐helices organized in two intertwined inverted repeats of seven transmembrane segments each and a large C‐terminal cytosolic domain referred to as the sulphate transporter and anti‐sigma factor antagonist (STAS) domain.…”

“…It is widely accepted that mammalian SLC26 members and their lower organism counterparts act as functional homodimers, although the dimerization mechanism was not unequivocally determined and probably differs among family members. Two swapped STAS domains have been determined as major determinants of the homodimeric assembly of murine Slc26a9, 122 Arabidopsis thaliana SULTR4;1 121 and BicA from Synechocystis sp, 119 while the STAS domain is not a requisite for SLC26Dg dimerization, which indeed relies on contacts between the transmembrane domain and is centred on TM14. 123 Some of the members of the SLC26 family show restricted tissue distribution, whereas other isoforms are more broadly expressed and orchestrate the ion transport across epithelia such as the intestine and kidney.…”