FIGURE 6.

Schematic model of the structural changes in early stage of GroES amyloid fibril formation. The region of Val⁴³-Leu⁵⁷ (denoted by a thick red line) has been identified as a region where structural changes occur early on during fibril formation. This region immediately precedes the fibril core region (Asp⁵⁸-Lys⁷⁴: denoted by blue arrows) and is apparently distinct from this region. This intermediate was monomeric, and the structural change was caused by the covalent rearrangement of Asn-Gly sequences. Especially, the formation of βAsp from Asn⁵¹ acts as a trigger for the following process. After formation of the intermediate species, a fibril nucleus may be formed fast at the adjacent core region, followed by very fast incorporation of disordered intact monomeric species (nucleus-dependent fibril extension). Therefore the mature amyloid fibrils of GroES contain both altered and unaltered molecular species. For details, see “Results” and “Discussion” sections.