SOD1 and amyotrophic lateral sclerosis: Introduction of cp173Venus, a circular permutation of the YFP variant Venus [57], to the aggregation-prone SOD1 carrying familial ALS-linked glycine 85 to arginine (SOD1-G85R) mutation enables emission of efficient FRET effect when proteasome activity is inhibited; under the same conditions, the use of conventional Venus as an acceptor resulted in no FRET [31].