Little is known today about the structure of full-length prions. We recently established, using solid-state NMR studies of the Ure2p and HET-s proteins, that prions show different architectures, and that the building principles between them can differ considerably. We here aim at the study of the Sup35 prion, which poses a formidable challenge considering its large size. Having demonstrated the important role of the globular domain, we here aim to study assembly in the context of the entire proteins, as opposed to fragments, and investigate on a molecular level the role of the functional C-terminal domain of the protein in fibril assembly. We aim thus to compare the structures of fibrillar Sup35NM and full-length Sup35p by solid state NMR. The fragment Sup35NM is often used as a model for the full-length prion. We will compare the structures of fibrillar Sup35NM and full-length Sup35p by solid state NMR and determine whether the structure of this fragment is indeed preserved in the context of the full-length fibril, or if it is different. This question is particularly relevant in the light of our previous results on the full-length HET-s and Ure2p prions, which show that the structure of the isolated prion and globular domains are not conserved in the context of the full-length prions. We will address this question by solid-state NMR, which is an emerging technique for the structural study of insoluble proteins. Important developments over the last decade have pushed this fast evolving technique to become a serious partner in structural biology. If it has been shown in proof-of-principle experiments that amyloid and prion structures can be determined by solid-state NMR methods, it is still difficult to obtain structures of full-length prions. The main difficulties are caused by the large size of these proteins, a property they also share with other insoluble proteins. However, many elements of the technology needed to tackle these problems are now available in the applicants’ laboratories and we propose to fully develop the NMR methodology and, in parallel, apply it to the yeast prion Sup35p that is made of 685 amino-acid residues. The key NMR methodology developed in the context of this proposal will allow us to establish structural models which will be confronted with the large body of biophysical and biochemical and functional knowledge to work out the relationship between structural and biological features of Sup35p. Besides, the protocols and techniques developed will also be applicable to other large proteins and should allow to open structural studies on other insoluble proteins.