Major prion protein, PrP or PRNP, of 253 aas and 3 possible TMSs, N-terminal, middle, and C-terminal. Its primary physiological function is unclear. It has cytoprotective activity against internal or environmental stresses and may play a role in neuronal development and synaptic plasticity. May be required for neuronal myelin sheath maintenance, but may play a role in iron uptake and iron homeostasis. Soluble oligomers are toxic to cultured neuroblastoma cells and induce apoptosis (Mani et al. 2003; Taylor et al. 2009; Wu et al. 2010).  The mouse orthologue (P04925), particularly the A116V mutant, forms ion channels in lipid membranes (Sabareesan et al. 2016). It's cell biology has been reviewed (Sarnataro et al. 2017).