A Twisted Four-Sheeted Model for an Amyloid Fibril

SummaryThe formation of amyloid fibers and their deposition in the body is a characteristic of a number of devastating human diseases. Here, we propose a structural model, based on X-ray diffraction data, for the basic structure of an amyloid fibril formed by using the variants of the B1 domain of IgG binding protein G of Streptococcus. The model for the fibril incorporates four β sheets in a bundle with a diameter of 45 Å. Its cross-section, or layer, consists of four strands, one strand from each sheet. Layers stack on top of each other to form the fibril, which has an overall helical twist with a periodicity of about 154 Å. Each strand interacts in a parallel fashion with the strands in the layers above and below it, in an infinite β sheet. Some geometric features of this model and the logic behind it may be applicable for constructing other related cross-β amyloid fibrils