Storage protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s are biological reserves of metal ions and amino acids, used by organisms. They are found in plant seeds, egg whites, and milk.

Ferritin

Ferritin

Ferritin is a ubiquitous intracellular protein that stores iron and releases it in a controlled fashion. The amount of ferritin stored reflects the amount of iron stored. The protein is produced by almost all living organisms, including bacteria, algae and higher plants, and animals...

 is an example of a storage protein that stores iron. Iron is a component of heme

Heme

A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...

, which is contained in the transport protein

Transport protein

A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. Transport proteins are integral membrane proteins; that is they exist within and span the membrane across which they...

 hemoglobin

Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

 and in cytochromes.

Some storage proteins store amino acids. Storage proteins' amino acids are used in embryonic development of animals or plants. Two amino acid storage proteins in animals are casein

Casein

Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....

 and ovalbumin

Ovalbumin

Ovalbumin is the main protein found in egg white, making up 60-65% of the total protein. Ovalbumin displays sequence and three-dimensional homology to the serpin superfamily, but unlike most serpins it is not a serine protease inhibitor...

.

Seeds, particularly of leguminous plants, contain high concentrations of storage proteins

Plant seed proteins

Plant seed proteins are small hydrophilic proteins some of which are structurally related. These proteins contains from 83 to 153 amino acid residues and may play a role in equipping the seed for survival, maintaining a minimal level of hydration in the dry organism and preventing the...

. Up to 25 percent of the dry weight of the seed can be composed of storage proteins.