9.B.7 The Putative Sulfate Transporter (CysZ) Family
The E. coli CysZ protein has a size of 253 aas with 5 TMS. It is a member of the DUF540 or COG2981 protein family. CysZ mutants are deficient in sulfate assimilation and are believed to be defective for sulfate uptake (Britton et al., 1983; Byrne et al., 1988; Parra et al., 1983). Thus CysZ may be a sulfate permease.
Distant homologues of about the same size are found in numerous bacteria and fungi (e.g., CAE76364 in Neurospora crassa and Q08219 in Saccharomyces cerevisiae), and many organisms have multiple CysZ homologues. In no case is the function established.
This 5TMS protein may be distantly related to 5TMS uptake proteins of the ABC superfamily.
The proposed transport process catalyzed by CysZ is:
SO4= (out) ⇋ SO4= (in)
