2.A.42 The Hydroxy/Aromatic Amino Acid Permease (HAAAP) Family
The HAAAP family includes three well-characterized aromatic amino acid:H+symport permeases of E. coli: a high affinity tryptophan-specific permease, Mtr, a low affinity tryptophan permease, TnaB, and a tyrosine-specific permease, TyrP, as well as two well-characterized hydroxy amino acid permeases, the serine permease, SdaC, of E. coli, and the threonine permease, TdcC, of E. coli. These proteins possess 403-443 amino acyl residues and exhibit eleven putative or established transmembrane
SdaC of E. coli (TC #2.A.42.2.1) is also called DcrA, and together with a periplasmic protein DcrB (P37620), it has been reported to play a role in phage DNA uptake in conjunction with an outer membrane receptor of the OMR family (TC #1.B.14). Thus, FhuA (TC #1.B.14.1.4) transports phage T5 DNA while BtuB (TC #1.B.14.3.1) transports phage C1 DNA (Samsonov et al., 2002). DcuB is a putative lipoprotein found only in enteric bacteria.
The generalized transport reaction catalyzed by proteins of the HAAAP family is:
Amino acid (out) + nH+ (out)