E-cadherin is a cell surface adhesion molecule that is expressed in both epithelial and endothelial tissues. In this study, an improved method for the simple production of the human E-cadherin-derived first repeat E-CAD I was developed by exporting it into the periplasmic space of Escherichia coli. Localization of the recombinant protein into the periplasm allowed the isolation of E-CAD1 without cell lysis. The N-terminus of E-CAD I is fused to a streptavidin-derived peptide to allow single-step purification using a Streptag affinity column. Optimal expression in LB medium produced 3.2mg/L while expression in minimal medium containing (NH4Cl)-N-15 as the sole source of nitrogen produced 4.2 mg/L purified N-15-labeled E-CAD1. Heteronuclear NMR spectroscopy confirmed that the purified E-CAD1 produced in this manner was correctly folded. The expression and purification protocol for unlabeled and isotopically labeled E-CAD1 permits rapid preparative production of this protein for mechanistic and structural studies. (C) 2002 Elsevier Science (USA). All rights reserved.