Homomeric Interaction of the STAS Domain in Sultr1;2

We recently reported the interaction of the STAS domain of SULTR1;2 and O-acetylserine(thiol) lyase (OASTL). This inter-protein interaction was initially identi fi ed in the yeast two hybrid system and was con fi rmed using other methods. Interestingly, we also found that the STAS domain (comprised of both the L and STAS' regions) of SULTR1;2 undergoes a homomeric interaction; an association between two STAS domains occurs as a consequence of a speci fi c interaction between the L and STAS' regions of the domain. The strength of this interaction depends on whether one or both of the interacting STAS partners contains an L region. A similar interaction was observed for the L and STAS' regions of SULTR3;1 but not of SULTR1;1. Lesions that alter the SULTR1;2 L and STAS' interactions do not appear to markedly impact sulfate transport activity, at least in yeast cells, although they may impact transport activity of SULTR1;2 in Arabidopsis. Hence, while regulation of sulfate transporter activity occurs through interactions of the transporter with OASTL, transporter activity may also be modulated by homomeric interactions in the STAS domain.