Homologues include thousands of diverse phage and bacterial proteins between 80 and 140 amino acyl residues (aas) in length that exhibit 3 to 4 transmembrane segments (TMSs).
[2] They derive from a wide range of bacterial and archaeal phyla including both Gram-negative and Gram-positive bacteria.
These proteins are related to the RDD family (TC# 9.B.45) in the conserved domain database.
[2] A representative list of proteins belonging to the T-A Hol family can be found in the Transporter Classification Database.
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