Structure and function of an Arabidopsis thaliana sulfate transporter
Lie Wang, Kehan Chen, Ming Zhou
Abstract
Abstract Plant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO 4 2− ) 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 SO 4 2− 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 SO 4 2− is coordinated by side-chain hydroxyls and backbone amides, and further stabilized electrostatically by the conserved Arg393 and two helix dipoles. Proton and SO 4 2− are co-transported by AtSULTR4;1 and a proton gradient significantly enhances SO 4 2− transport. Glu347, which is ~7 Å from the bound SO 4 2− , 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 SO 4 2− transport, suggesting a regulatory function of the STAS domain.