The STAS (after Sulphate Transporter and AntiSigma factor antagonist) domain is found in the C terminal region of Sulphate transporters and bacterial antisigma factor antagonists. It has been suggested that this domain may have a general NTP binding function [2].

1: Solution structure of SpoIIAA, a phosphorylatable component of the system that regulates transcription factor sigmaF of Bacillus subtilis. Kovacs H, Comfort D, Lord M, Campbell ID, Yudkin MD; Proc Natl Acad Sci U S A 1998;95:5067-5071. PMID:9560229

2: The STAS domain - a link between anion transporters and antisigma-factor antagonists Aravind L, Koonin EV; CurrBiol 2000;10:53-55. PMID:10662676