The peptide hormone glucagon forms amyloid fibrils with two coexisting beta-strand conformations.
Gelenter, M.D., Smith, K.J., Liao, S.Y., Mandala, V.S., Dregni, A.J., Lamm, M.S., Tian, Y., Xu, W., Pochan, D.J., Tucker, T.J., Su, Y., Hong, M.(2019) Nat Struct Mol Biol 26: 592-598
- PubMed: 31235909 
- DOI: 10.1038/s41594-019-0238-6
- Primary Citation of Related Structures:  
6NZN - PubMed Abstract: 
Glucagon and insulin maintain blood glucose homeostasis and are used to treat hypoglycemia and hyperglycemia, respectively, in patients with diabetes. Whereas insulin is stable for weeks in its solution formulation, glucagon fibrillizes rapidly at the acidic pH required for solubility and is therefore formulated as a lyophilized powder that is reconstituted in an acidic solution immediately before use ...