Amnionless is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''AMN''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Function

A complex of amnionless and

cubilin Cubilin is a protein that in humans is encoded by the ''CUBN'' gene. Function Cubilin (CUBN) acts as a receptor for intrinsic factor-vitamin B12 complexes. The role of receptor is supported by the presence of 27 CUB domains. Cubilin shows a r ...

forms the

cubam Cubam, is the term used to refer to a multi-ligand receptor located in the terminal ileum, specializing in absorption of vitamin B12. Cubam is essentially composed of amnionless (AMN), and cubilin. Cubilin is essential as a cell receptor recogni ...

receptor. The protein encoded by this gene is a

type I transmembrane protein A single-pass membrane protein also known as single-spanning protein or bitopic protein is a transmembrane protein that spans the lipid bilayer only once. These proteins may constitute up to 50% of all transmembrane proteins, depending on the or ...

. It is thought to modulate

bone morphogenetic protein Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Professor Marshall Urist and Professor Hari Reddi discovered their ability to induce the formation of bone and cartilage, BMPs are now ...

(BMP) receptor function by serving as an accessory or coreceptor, and thus facilitates or hinders BMP binding. It is known that the mouse AMN gene is expressed in the extraembryonic visceral

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...

layer during

gastrulation Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as ...

, but it is found to be mutated in amnionless mouse. The encoded protein has sequence similarity to short gastrulation (Sog) and

procollagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

IIA proteins in

Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...

Clinical significance

Mutations of the AMN gene may cause

Imerslund–Gräsbeck syndrome Imerslund–Gräsbeck syndrome is a rare autosomal recessive, familial form of vitamin B12 deficiency caused by malfunction of the "'' Cubam''" receptor located in the terminal ileum. This receptor is composed of two proteins, amnionless (AMN), an ...

Function

Clinical significance

References

External links

Further reading