Tardigrade specific proteins

Tardigrade specific proteins (TDPs) are specific types of Intrinsically Disordered Proteins (IDPs) that are seen in tardigrades. They are most notably used to help them survive desiccation which makes them very extremotolerant.
Taxonomy.
TDPs are found in the clade Tardigrada and more specifically, the branch called Parachela.
Function.
TDPs are a type of IDP. This means that they have no specific shape unlike traditional folded proteins. There are three families of TDPs. They are each named after where the protein is localized within a cell. These proteins are similar to Late Embryogenesis Abundant (LEA) proteins, except for their specificity to tardigrades. The three families do not resemble each other and are found to be expressed or enriched during desiccation. Unlike traditional proteins, IDPs are not found to precipitate out of solution or denature during high heat.
Discovery of the Cytoplasmic and Secreted Abundant Heat Soluble proteins were found when searching for LEA proteins in tardigrades.
Types.
Cytoplasmic.
Cytoplasmic Abundant Heat Soluble (CAHS) proteins have been seen to be highly expressed in response to desiccation. The oldest theory in the mechanism of CAHS proteins is the vitrification hypothesis in which when the organism dries, the viscosity within the cell would increase so much that denaturation and membrane fusion in proteins would stop. A second theory is the water replacement theory in which the CAHS proteins replaces water in the proteins, protecting the bonds that would normally be affected by the hydrogen in water.
Secreted.
Secreted Abundant Heat Soluble (SAHS) proteins have been noted to be similar to fatty acid binding proteins. They are often secreted into media and often associated with special extracellular structures.
Mitochondrial.
Mitochondrial Abundant Heat Soluble (MAHS) proteins are localized in the mitochondria and are responsible for protecting the mitochondria during desiccation. It is thought that the MAHS proteins act to replace water in the membrane of the mitochondria, preventing uneven rehydration and breaking of the membrane.