Figure 3.

M8 presents several different intermediates during polymerization, which can be detected by transmission electronic microscopy (TEM). (A) Structure of HET-s_(218-289) fibers obtained by solid-NMR in a previous study (18). (B) We did not observe any intermediates formed by the WT protein during the time period indicated, but detected rapidly the appearance of protofibrils of various sizes, fibers, bundles of fibers, or protein plaques of amorphous aggregates. The picture presents a large bundle at 30 min. (C) Analysis of M8 polymerization over time showed the appearance of several different intermediates characterized by round oligomers, followed by short fibers of ∼100 × 10 nm, which then seemed to fuse laterally to form larger aggregates that were able to precipitate. (D) Size of round oligomers was analyzed, and was ∼10 nm in diameter, consistent with the width of a basic M8 fiber.