Fibrillogenic propensity of the GroEL apical domain: A Janus-faced minichaperone

► The fibrillogenic region of GroEL locates in its apical domain. ► Both GroEL and the apical domain can form amyloid-like fibrils in a physiological buffer. ► Isolated apical domain inhibits fibril-growth of human β2-microglobulin.