Figure 6. Schematic representations of a proposed structure for the Nt domain of Type A and Type P models. (a) A flattened representation of the β-strands for one subunit’s contribution to two Type A concentric β-barrels as viewed from outside the barrels. In some models S5 is part of the inner barrel and Sy7 is not always an extension of Sy6 and Sy8. (b) A flattened representation of the β-strands for one subunit’s contribution to two Type P concentric β-barrels. Only Nt segments are shown because relative positions of NAC strands vary among models. (c) Schematic of the conformation of a monomer in putative concentric Type P β-barrels as viewed down the central axis of the barrels. The strands within each barrel are parallel and oriented in opposite directions in the adjacent barrels. (d) Illustration of intermeshing pleats for concentric β-barrels that have pleats with similar pitches. The gold cylinder represents an inner barrel with the brown circles representing outwardly oriented side-chains of two adjacent pleats. The gray cylinder represents a surrounding barrel with the black dots representing side-chains of a central pleat that fits between the two pleats of the inner barrel. (e) Side view of sequentially adjacent strands approximating how their side-chains may pack between one another in Type P models. The asterisks indicate where the sequence of β-syn differs from that of α-Syn.