Abstract
Sulfate transporters in plants and animals are structurally conserved and have an amino-terminal domain that functions in transport and a carboxyl-terminal region that has been designated the STAS domain. The STAS domain in sulfate transporters has significant similarity to bacterial anti-sigma factor antagonists. To determine if the STAS domain has a role in controlling the activity of sulfate transporters, their stability, or their localization to the plasma membrane, we examined the effect of deleting or modifying the STAS domain of dominant sulfate transporters in roots of Arabidopsis thaliana. The A. thaliana Sultr1;2 and Sultr1;1 sulfate transporters rescue the methionine-dependent growth phenotype of the yeast sulfate transporter mutant strain CP154-7B. Constructs of Sultr1;2 in which the STAS domain was deleted (DeltaSTAS) resulted in synthesis of a truncated polypeptide that was unable to rescue the CP154-7B phenotype. The inability of these constructs to rescue the mutant phenotype probably reflected both low level cellular accumulation of the transporter and the inability of the truncated protein to localize to the plasma membrane. Fusing the STAS domain from other sulfate transporters to Sultr1;2 DeltaSTAS constructs restored elevated accumulation and plasma membrane localization, although the kinetics of sulfate uptake in the transformants were markedly altered with respect to transformants synthesizing wild-type Sultr1;2 protein. These results suggest that the STAS domain is essential, either directly or indirectly, for facilitating localization of the transporters to the plasma membrane, but it also appears to influence the kinetic properties of the catalytic domain of transporters.
Highlights
Sulfate transporters constitute a large family of anion transporters (SLC26 or SulP family, transport commission no. 2.A.53) present in bacteria, fungi, plants, and mammals [1,2,3]
Rescue of Yeast sul1 sul2 Mutant by A. thaliana Sulfate Transporter Genes and Requirement for the STAS Domain—A S. cerevisiae mutant null for Sul1 and Sul2 sulfate transporter genes, designated CP154-7B, is unable grow on medium containing sulfate as the sole sulfur source, but grows rapidly in medium supplemented with methionine [18]
Previous work demonstrated that the A. thaliana sulfate transporters Sultr1;2 and Sultr1;1 were able to complement the yeast CP154-7B mutant, and this heterologous system was used to determine the kinetic characteristics associated with this and other transporters [22, 23]
Summary
These results, plus the results that correlate STAS domain mutations with specific diseases in humans, suggest that the STAS domain and its orientation with respect to the catalytic domain may contribute to the activity/regulation associated with anion transporters. Function of STAS Domain in Sulfate Transporters transporters and determined their subcellular locations These studies demonstrate that the STAS domain and the region that links the STAS domain to the catalytic domain are necessary, either directly or indirectly, for the correct and/or stable localization of the Sultr1;2 protein in the yeast plasma membrane, and that STAS domains from different sulfate transporter proteins can markedly affect the kinetic characteristics of transporter activity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
