The role of water in amyloid aggregation kinetics

The role of water in protein function and aggregation is highly important and may hold some answers to understanding initiation of misfolding diseases such as Parkinson's, Alzheimer's and Huntington's where soluble intrinsically disordered proteins (IDPs) aggregate into fibrillar structures. IDPs are highly dynamic and have larger solvent exposed areas compared to globular proteins, meaning they make and break hydrogen bonds with the surrounding water more frequently. The mobility of water can be altered by presence of ions, sugars, osmolytes, proteins and membranes which differ in different cell types, cell compartments and also as cells age. A reduction in water mobility and thus protein mobility enhances the probability that IDPs can associate to form intermolecular bonds and propagate into aggregates. This poses an interesting question as to whether localised water mobility inside cells can influence the propensity of an IDP to aggregate and furthermore whether it can influence fibril polymorphism and disease outcome.

Role of water in protein folding, oligomerization, amyloidosis and miniprotein

The essential involvement of water in most fundamental extra-cellular and intracellular processes of proteins is critically reviewed and evaluated in this article. The role of water in protein behavior displays structural ambivalence; it can protect the disordered peptide-chain by hydration or helps the globular chain-folding, but promotes also the protein aggregation, as well (see: diseases). A variety of amyloid diseases begins as benign protein monomers but develops then into toxic amyloid aggregates of fibrils. Our incomplete knowledge of this process emphasizes the essential need to reveal the principles of governing this oligomerization. To understand the biophysical basis of the simpler in vitro amyloid formation may help to decipher also the in vivo way. Nevertheless, to ignore the central role of the water's effect among these events means to receive an uncompleted picture of the true phenomenon. Therefore this review represents a stopgap role, because the most published studies--with a few exceptions--have been neglected the crucial importance of water in the protein research. The following questions are discussed from the water's viewpoint: (i) interactions between water and proteins, (ii) protein hydration/dehydration, (iii) folding of proteins and miniproteins, (iv) peptide/protein oligomerization, and (v) amyloidosis.