Amyloid-beta peptide 42 (A beta 42) mediates neuronal degeneration in Alzheimer's disease (AD). We sought to produce recombinant A beta 42 as an ubiquitin extension. A synthetic oligonucleotide encoding A beta 42 was constructed and cloned as an extended polypeptide of hexahistidine-tagged ubiquitin (H(6)Ub) using the pET vector. Isopropyl-beta-D-thiogalactopyranoside induction of transformed Escherichia coli resulted in the production of large amounts of insoluble H(6)Ub-A beta 42 fusion protein. H(6)Ub-A beta 42 was solubilized in 8 M urea and applied to a nickel-nitrilotri acetic acid affinity column for purification. Column washing removed the urea and soluble H(6)Ub-A beta 42 was eluted, indicating that covalently attached ubiquitin prevented A beta 42 from aggregating. A beta 42 was cleaved from H(6)Ub using recombinant yeast ubiquitin hydrolase-1 (YUH-1) and purified using reverse-phase chromatography. The recombinant A beta 42 prepared in this study has the same toxic effect on human neuroblastoma SH-SY5Y cells comparing with chemically synthesized, commercial one. The peptide yield was more than 4mg/L culture, indicating this ubiquitin fusion technique is an attractive method for production of aggregation-prone peptides such as A beta 42. (c) 2005 Elsevier Inc. All rights reserved.