Polar residues in a conserved motif spanning helices 1 and 2 are functionally important in the SulP transporter family.

The SulP family (including the SLC26 family) is a diverse family of anion transporters found in all domains of life, with different members transporting different anions. We used sequence and bioinformatics analysis of helices 1 and 2 of SulP family members to identify a conserved motif, extending the previously defined 'sulfate transporter motif'. The analysis showed that in addition to being highly conserved in both sequence and spacing, helices 1 and 2 contain a significant number of polar residues and are predicted to be buried within the protein interior, with at least some faces packed closely against other helices.