The NhaB family
TC# 2.A.34
belongs to the ion transporter (IT) superfamily. A representative list of proteins belonging to the NhaB family can be found in th
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 ''Mycobacterium leprae'' (also known as the leprosy bacillus or Hansen's bacillus), is one of the two species of bacteria that cause Hansen’s disease (leprosy), a chronic but curable infectious disease that damages the peripheral nerves and ...

'' (spP46838) which is also homologous to a member of arsenate resistance pumps of

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

and

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

s
TC# 3.A.4
. Only

gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

l proteins have been functionally characterized. The ''E. coli'' NhaB is 58% identical to the orthologous ''

Vibrio alginolyticus ''Vibrio alginolyticus'' is a Gram-negative marine bacterium. It is medically important since it causes otitis and wound infection. It is also present in the bodies of animals such as pufferfish, where it is responsible for the production of ...

'' Na⁺/H⁺ antiporter. 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 The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...

. A centrally located aspartyl residue in the 3rd TMS is conserved in all members of the family and important for activity. The generalized transport reaction catalyzed by NhaB of ''E. coli'' is:

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

References

Protein families Membrane proteins Transmembrane proteins Transmembrane transporters Transport proteins Integral membrane proteins {{membrane-protein-stub

See also

References