Ammonia transporters are structurally related membrane transport proteins called Amt proteins (ammonia transporters, bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and plants), methylammonium/ammonium permeases (MEPs, in yeast

Yeast

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

) or RhAG

RHAG

Rh-associated glycoprotein is an ammonia transporter protein that in humans is encoded by the RHAG gene. RHAG has also recently been designated CD241 . Mutations in the RHAG gene can cause stomatocytosis....

, RhBG

RHBG

Rh family, B glycoprotein, also known as RHBG, is an ammonia transporter protein which in humans is encoded by the RHBG gene.- Function :...

, and RhCG

RHCG

Rh family, C glycoprotein, also known as RHCG, is a protein which in humans is encoded by the RHCG gene.- Function :RHCG plays a critical role in ammonium handling and pH homeostasis in the kidney. The structure of the RHCG protein indicates that it has a hydrophobic ammonia-conducting channel thus...

 Rh family

Rh blood group system

The Rh blood group system is one of thirty current human blood group systems. Clinically, it is the most important blood group system after ABO. At Present, the Rh blood group system consists of 50 defined blood-group antigens, among which the 5 antigens D, C, c, E, and e are the most important...

 members in mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s. The RhAG, RhBG and RhCG proteins constitute solute carrier family

Solute carrier family

The solute carrier group of membrane transport proteins include over 300 members organized into 51 families. The SLC gene nomenclature system was originally proposed by the Human Genome Organization and is the basis for the official HUGO names of the genes that encode these transporters...

 42. The three dimensional structure of the ammonia transport protein AmtB from Escherichia coli

Escherichia coli

Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

was determined by x-ray crystallography

X-ray crystallography

X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...

. The structure has a hydrophobic ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 channel. The human RhCG ammonia transporter was found to have a similar ammonia-conducting channel structure. It was proposed that the erythrocyte Rh complex is a heterotrimer of RhAG, RhD

RHD (gene)

Rh blood group, D antigen also known as Rh polypeptide 1 or cluster of differentiaion 240D is a protein that in humans is encoded by the RHD gene....

, and RhCE

RHCE (gene)

Blood group Rh polypeptide is a protein that in humans is encoded by the RHCE gene. RHCE has also recently been designated CD240CE ....

 subunits in which RhD and RhCE might play roles in anchoring the ammonia-conducting RhAG subunit to the cytoskeleton. Based on reconstitution experiments, purified RhCG subunits alone can function to transport ammonia. RhCG is required for normal acid excretion

Renal tubular acidosis

Renal tubular acidosis is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine. When blood is filtered by the kidney, the filtrate passes through the tubules of the nephron, allowing for exchange of salts, acid...

 by the mouse kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 and epididymis

Epididymis

The epididymis is part of the male reproductive system and is present in all male amniotes. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. A similar, but probably non-homologous, structure is found in cartilaginous...

.