Intrinsically unstructured proteins and their function: a new view of protein structure and plant responses to stress

Abstract

The dogma that relates the function of a protein with a defined three-dimensional structure has been challenged in recent years by the discovery and characterization of a set of proteins known as unstructured or disordered proteins. These proteins have a high structural flexibility which allows them to adopt different structures and therefore recognize different ligands while retaining their specificity. Proteins of this type, which are highly hydrophilic and accumulate under water deficit (drought, salinity, freezing) have been recently characterized and named hydrophilins. In plants, the best characterized hydrophilins are the LEA proteins (for Late Embryogenesis Abundant), which accumulate abundantly in the dry seed and in vegetative tissues when plants are exposed to water-limited environments. Recent evidence has shown that LEA proteins are required for plants to tolerate and adapt to conditions of low-water availability. This review describes the most relevant data regarding their structural flexibility and how this is affected by environmental conditions. Also, it addresses information related to their possible functions in plant cells that are exposed to water deficit.