The formation of amyloid fibrils by relaxin

Abstract

The amyloid diseases involve the deposition of normally soluble proteins in the form of stable insoluble fibrils in a variety of tissues. Amyloid formation is associated with a number of conditions including Alzheimer’s disease, Creutzfeldt-Jakob Disease (CJD) and late-onset diabetes [1,2]. In addition to the amyloidogenic proteins associated with disease, it is now becoming clear that the formation of fibrils is a fundamental property of the polypeptide backbone [3,4,5,6]. A wide variety of structurally and functionally unrelated proteins are now known to self-associate into amyloid structures [7,8], yet the fibrils formed by different proteins share a common fundamental architecture. Amyloid is characterised by a typical ‘cross-13’ X-ray diffraction pattern indicative of a stacked 13-sheet structure in which the strands are arranged perpendicular to the fibril axis; by a long, unbranched appearance under electron microscopy; and by staining with the dye Congo Red, which exhibits a green birefringence when viewed under polarised light [9].