Hormone history mirrors prion morphology
Structural studies of insulin shed light on the prion strain phenomenon and suggest a new approach to biomaterial synthesis.
The insulin protein forms in water as one type of amyloid fibril (type A), but Wojciech Dzwolak at the Polish Academy of Sciences, Sokolowska, and colleagues found that it adopts a more 'curvy' stacked form (type B) when formed in the presence of ethanol.
Dzwolak's team found that insulin types A and B behave rather like prions. When type B is added to an insulin solution in pure water, the type B proteins act as a template for the formation of further type B proteins.
'It is only the template that matters,' Dzwolak said, 'not the presence of ethanol, which favours type B, or its absence, which favours type A.' The type of insulin formed is controlled by the history of the template.
The findings have medical and technical implications. Amyloid deposits in the brain characterise a range of poorly understood neuropathologies, from Alzheimer's to prion diseases. On the technological front, fibril morphology could be controlled for the synthesis of biomaterials on the basis of 'solvational history,' suggests Dzwolak.