Homoserine/threonine resistance transporter

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Homoserine lactone efflux protein

The resistance to homoserine/threonine (RhtB) family (TC# 2.A.76) belongs to the lysine exporter (LysE) superfamily of transporters.[1] Hundreds of sequenced proteins, derived from Gram-negative and Gram-positive bacteria as well as archaea, comprise the RhtB family, but few of these proteins are functionally characterized.[2]


The first two members of the RhtB family to be characterized functionally were the RhtB (TC# 2.A.76.1.1) and RhtC (TC# 2.A.76.1.2) permeases of E. coli.[3][4]

E. coli possesses five paralogues, and a large region of one of them (YahN of E. coli; TC# 2.A.76.1.3) exhibits significant sequence similarity to YggA of E. coli (TC# 2.A.75.1.2), an established member of the LysE family (TC #2.A.75).

The PSI-BLAST program groups the LysE family (TC# 2.A.75), the RhtB family and the CadD family (TC #2.A.77) together. These proteins are all of about the same size and apparent topology, further suggesting a common evolutionary origin.[2]

The leucine exporter homologue (YeaS or LeuE; TC# 2.A.76.1.5) exports leucine and several other neutral, hydrophobic amino acids.[5]

A representative list of proteins belonging to the RhtB family can be found in the Transporter Classification Database.

General transport reaction[edit]

The transport reaction presumably catalyzed by members of the RhtB family is:[6]

amino acid (in) + nH+ (out) ⇌ amino acid (out) + nH+ (in)

See also[edit]


  1. ^ Tsu BV, Saier MH (2015-01-01). "The LysE Superfamily of Transport Proteins Involved in Cell Physiology and Pathogenesis". PLOS One. 10 (10): e0137184. doi:10.1371/journal.pone.0137184. PMC 4608589. PMID 26474485.
  2. ^ a b Vrljic M, Garg J, Bellmann A, Wachi S, Freudl R, Malecki MJ, Sahm H, Kozina VJ, Eggeling L, Saier MH, Eggeling L, Saier MH (November 1999). "The LysE superfamily: topology of the lysine exporter LysE of Corynebacterium glutamicum, a paradyme for a novel superfamily of transmembrane solute translocators". Journal of Molecular Microbiology and Biotechnology. 1 (2): 327–36. PMID 10943564.
  3. ^ Aleshin VV, Zakataeva NP, Livshits VA (April 1999). "A new family of amino-acid-efflux proteins". Trends in Biochemical Sciences. 24 (4): 133–5. doi:10.1016/s0968-0004(99)01367-5. PMID 10322417.
  4. ^ Zakataeva NP, Aleshin VV, Tokmakova IL, Troshin PV, Livshits VA (June 1999). "The novel transmembrane Escherichia coli proteins involved in the amino acid efflux". FEBS Letters. 452 (3): 228–32. doi:10.1016/s0014-5793(99)00625-0. PMID 10386596.
  5. ^ Kutukova EA, Livshits VA, Altman IP, Ptitsyn LR, Zyiatdinov MH, Tokmakova IL, Zakataeva NP (August 2005). "The yeaS (leuE) gene of Escherichia coli encodes an exporter of leucine, and the Lrp protein regulates its expression". FEBS Letters. 579 (21): 4629–34. doi:10.1016/j.febslet.2005.07.031. PMID 16098526.
  6. ^ "TCDB » SEARCH". www.tcdb.org. Retrieved 2016-02-25.

As of 25 February 2016, this article is derived in whole or in part from Transporter Classification Database. The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL. All relevant terms must be followed. The original text was at "2.A.76 The Resistance to Homoserine/Threonine (RhtB) Family".