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2.A.26 The Branched Chain Amino Acid:Cation Symporter (LIVCS) Family

Characterized members of this family transport all three of the branched chain aliphatic amino acids (leucine (L), isoleucine (I) and valine (V)). They are found in Gram-negative and Gram-positive bacteria and function by a Na+ or H+ symport mechanism. They possess about 440 amino acyl residues and display 12 putative transmembrane helical spanners. Some of these transporters can also take up threonine (Khozov et al. 2023).  BrnQ of E. coli has been reported to be able to take up threonine but not serine.

The generalized transport reaction is:

[L, I, V or T] (out) + [Na+ or H+] (out)  [L, I, V or T] (in) + [Na+ or H+] (in)

This family belongs to the: APC Superfamily.

References associated with 2.A.26 family:

Braun, P.R., H. Al-Younes, J. Gussmann, J. Klein, E. Schneider, and T.F. Meyer. (2008). Competitive inhibition of amino acid uptake suppresses chlamydial growth: involvement of the chlamydial amino acid transporter BrnQ. J. Bacteriol. 190: 1822-1830. 18024516
Guardiola, J., M. De Felice, T. Klopotowski, and M. Iaccarino. (1974). Mutations affecting the different transport systems for isoleucine, leucine, and valine in Escherichia coli K-12. J. Bacteriol. 117: 393-405. 4590465
Khozov, A.A., D.M. Bubnov, E.D. Plisov, T.V. Vybornaya, T.V. Yuzbashev, G. Agrimi, E. Messina, A.A. Stepanova, M.D. Kudina, N.V. Alekseeva, A.I. Netrusov, and S.P. Sineoky. (2023). A study on L-threonine and L-serine uptake in K-12. Front Microbiol 14: 1151716. 37025642
Radi, M.S., J.E. SalcedoSora, S.H. Kim, S. Sudarsan, A.V. Sastry, D.B. Kell, M.J. HerrgÄrd, and A.M. Feist. (2022). Membrane transporter identification and modulation via adaptive laboratory evolution. Metab Eng 72: 376-390. 35598887
Reizer, J., A. Reizer and M.H. Saier, Jr. (1994). A functional superfamily of sodium/solute symporters. Biochim. Biophys. Acta 1197: 133-166. 8031825
Stucky, K., A. Hagting, J.R. Klein, H. Matern, B. Henrich, W.N. Konings and R. Plapp (1995). Cloning and characterization of brnQ, a gene encoding a low-affinity, branched-chain amino acid carrier in Lactobacillus delbruckii subsp. lactis DSM7290. Mol. Gen. Genet. 249: 682-690. 8544834
Tauch, A., T. Hermann, A. Burkovski, R. Krämer, A. Pühler and J. Kalinowski (1998). Isoleucine uptake in Corynebacterium glutamicum ATCC 13032 is directed by the brnQ gene product. Arch. Microbiol. 169: 303-312. 9531631
Trip, H., N.L. Mulder, and J.S. Lolkema. (2013). Cloning, expression, and functional characterization of secondary amino acid transporters of Lactococcus lactis. J. Bacteriol. 195: 340-350. 23144255