Alzheimer's disease (AD) is the most common type of dementia in elderly people. Senile plaques, a pathologic hallmark of AD, are composed of amyloid beta peptide (A beta). A beta aggregation produces toxic oligomers and fibrils, causing neuronal dysfunction and memory loss. A beta is generated from two sequential proteolytic cleavages of a membrane protein, amyloid precursor protein (APP), by beta- and gamma-secretases. The transmembrane (TM) domain of APP, APPTM, is the substrate of gamma-secretase for A beta production. The interaction between APPTM and gamma-secretase determines the production of different species of A beta. Although numerous experimental and theoretical studies of APPTM structure exist, experimental 3D structure of APPTM has not been obtained at atomic resolution. Using the pETM41 vector, we successfully expressed an MBP-APPTM fusion protein. By combining Ni-NTA chromatography, TEV protease cleavage, and reverse phase HPLC (RP-HPLC), we purified isotopically-labeled APPTM for NMR studies. The reconstitution of APPTM into micelles yielded high quality 2D (15)N-(1)H HSQC spectra. This reliable method for APPTM expression and purification lays a good foundation for future structural studies of APPTM using NMR. (C) 2011 Elsevier Inc. All rights reserved.