| 摘要 |
Tardigrades, also known as water bears, possess an extraordinary ability to survive for extended periods under harsh conditions like extreme dryness, low temperatures, and low pressure. Under such condition, tardigrades enter into a state of cryptobiosis, where they undergo dehydration, body shrinkage, and metabolic halting, enabling them to endure extreme conditions for years. Once the environment improves, the cells or body in cryptobiosis can rehydrate and recover. Tardigrades owe this ability in part to some unique tardigrade disordered proteins (TDP), also called heat-soluble proteins, which safeguard their cells during dehydration by reshaping their structure to fix liquid water during desiccation. However, research on these proteins is still in its nascent stages, and the thorough mechanistic investigations are lacking. This article provides a concise overview of these unique proteins found in tardigrades, including their sequence, physicochemical properties, potential biological functions, and mechanisms. Currently, there are 3 major families of TDPs known as cytosolic-abundant heat-soluble proteins (CAHS), secretory-abundant heat-soluble proteins (SAHS), and mitochondrial-abundant heat-soluble proteins (MAHS). A large fraction of these proteins contain are intrinsic disorder regions that are critical to their function in desiccation tolerance. The CAHS proteins contain a long alpha-helix and two flanking intrinsic disordered regions, and play roles in the vitrification process during desiccation. The SAHS proteins contain a central beta-barrel and a helix-turn-helix cap motif, and they may form a protective network outside the cells under extreme environment. The MAHS proteins contain a loosely organized core consist of 5 alpha-helix and the flanking region of disordered motifs, and their major roles is to protect the mitochondrial during desiccation. The unique structure and property of these TDPs may help to develop new technology in aiding higher animals to adapt to extreme environments, such as low temperatures and low oxygen. The ability of human cells to undergo cryptobiosis and reversible recovery in extreme environments has critical implications in fields like medicine, space exploration, and interstellar immigration. |
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