NhaB family

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The NhaB family (TC# 2.A.34) belongs to the ion transporter (IT) superfamily. [1] A representative list of proteins belonging to the NhaB family can be found in the Transporter Classification Database.

NhaB homologues are usually about 500 aminoacyl residues (aas) in length and possess about 12 transmembrane alpha-helical spanners (TMSs), although some members differ in their number of TMSs. NhaB homologues also exhibit a region with limited sequence similarity to a 46 kDa membrane protein of unknown function from Mycobacterium leprae (spP46838) which is also homologous to a member of arsenate resistance pumps of bacteria, archaea and eukaryotes (TC# 3.A.4). Only gram-negative bacterial proteins have been functionally characterized.

The E. coli NhaB is 58% identical to the orthologous Vibrio alginolyticus Na+/H+ antiporter. [2] Although the latter protein is predicted to exhibit 10 TMSs, construction of NhaB-phoA fusions led to evidence for a 9 TMS model with the N-terminus in the cytoplasm and the C-terminus in the periplasm. [3] A centrally located aspartyl residue in the 3rd TMS is conserved in all members of the family and important for activity. [4]

The generalized transport reaction catalyzed by NhaB of E. coli is:

2 Na+ (in) + 3 H+ (out) ⇌ 2 Na+ (out) + 3 H+ (in).

See also

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<span class="mw-page-title-main">Sodium-solute symporter</span> Group of transport proteins

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Divalent anion:Na+ symporters were found in bacteria, archaea, plant chloroplasts and animals.

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<span class="mw-page-title-main">NhaA family</span> Family of transport proteins

Na+/H+ antiporter A (NhaA) family (TC# 2.A.33) contains a number of bacterial sodium-proton antiporter (SPAP) proteins. These are integral membrane proteins that catalyse the exchange of H+ for Na+ in a manner that is highly pH dependent. Homologues have been sequenced from a number of bacteria and archaea. Prokaryotes possess multiple paralogues. A representative list of the proteins that belong to the NhaA family can be found in the Transporter Classification Database.

The NhaC family belongs to the Ion Transporter (IT) Superfamily. A representative list of proteins belonging to the NhaC family can be found in the Transporter Classification Database.

The NhaD family belongs to the Ion Transporter (IT) Superfamily. A representative list of proteins belonging to the NhaD family can be found in the Transporter Classification Database.

The NhaE family belongs to the Ion Transporter (IT) Superfamily, which has an end. A representative list of proteins belonging to the NhaE family can be found in the Transporter Classification Database.

<span class="mw-page-title-main">Monovalent cation:proton antiporter-1</span> Family of proteins

The Monovalent Cation:Proton Antiporter-1 (CPA1) Family (TC# 2.A.36) is a large family of proteins derived from Gram-positive and Gram-negative bacteria, blue-green bacteria, archaea, yeast, plants and animals. The CPA1 family belongs to the VIC superfamily. Transporters from eukaryotes have been functionally characterized to catalyze Na+:H+ exchange. Their primary physiological functions are thought to be in (1) cytoplasmic pH regulation, extruding the H+ generated during metabolism, and (2) salt tolerance (in plants), due to Na+ uptake into vacuoles. Bacterial homologues have also been found to facilitate Na+:H+ antiport, but some also catalyze Li+:H+ antiport or Ca2+:H+ antiport under certain conditions.

The Monovalent Cation (K+ or Na+):Proton Antiporter-3 (CPA3) Family (TC# 2.A.63) is a member of the Na+ transporting Mrp superfamily. The CPA3 family consists of bacterial multicomponent K+:H+ and Na+:H+ antiporters. The best characterized systems are the PhaABCDEFG system of Sinorhizobium meliloti (TC# 2.A.63.1.1) that functions in pH adaptation and as a K+ efflux system, and the MnhABCDEFG system of Staphylococcus aureus (TC# 2.A.63.1.3) that functions as a Na+ efflux Na+:H+ antiporter.

The inorganic phosphate transporter (PiT) family is a group of carrier proteins derived from Gram-negative and Gram-positive bacteria, archaea, and eukaryotes.

References

  1. ↑ Prakash, Shraddha; Cooper, Garret; Singhi, Soumya; Saier, Milton H. (2003-12-03). "The ion transporter superfamily". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1618 (1): 79–92. doi: 10.1016/j.bbamem.2003.10.010 . ISSN   0006-3002. PMID   14643936.
  2. ↑ Pinner, E.; Padan, E.; Schuldiner, S. (1992-06-05). "Cloning, sequencing, and expression of the nhaB gene, encoding a Na+/H+ antiporter in Escherichia coli". The Journal of Biological Chemistry. 267 (16): 11064–11068. doi: 10.1016/S0021-9258(19)49875-X . ISSN   0021-9258. PMID   1317851.
  3. ↑ Enomoto, H.; Unemoto, T.; Nishibuchi, M.; Padan, E.; Nakamura, T. (1998-03-06). "Topological study of Vibrio alginolyticus NhaB Na+/H+ antiporter using gene fusions in Escherichia coli cells". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1370 (1): 77–86. doi: 10.1016/s0005-2736(97)00245-9 . ISSN   0006-3002. PMID   9518558.
  4. ↑ Nakamura, T.; Fujisaki, Y.; Enomoto, H.; Nakayama, Y.; Takabe, T.; Yamaguchi, N.; Uozumi, N. (2001-10-01). "Residue aspartate-147 from the third transmembrane region of Na(+)/H(+) antiporter NhaB of Vibrio alginolyticus plays a role in its activity". Journal of Bacteriology. 183 (19): 5762–5767. doi:10.1128/JB.183.19.5762-5767.2001. ISSN   0021-9193. PMC   95471 . PMID   11544242.

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