The TRPM2 protein is a heat-activated sensor of oxidative stress which has been implicated in diseases such as diabetes. Using single-particle analysis of electron microscope images, we are able to present a three-dimensional structure to further the understanding of its physiological role.
Abstract from: THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 282, NO. 51, pp. 36961–36970, December 21, 2007
Three-dimensional Reconstruction Using Transmission Electron Microscopy Reveals a Swollen, Bell-shaped Structure of Transient Receptor Potential Melastatin Type 2 Cation Channel
Yuusuke Maruyama‡§, Toshihiko Ogura‡¶, Kazuhiro Mio‡, Shigeki Kiyonaka, Kenta Kato, Yasuo Mori, and Chikara Sato‡§1
From the ‡Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-4, Tsukuba, Ibaraki 305-8568, the §Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai,Tsukuba, Ibaraki 305-8577, ¶PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, and the Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
Transient receptor potential melastatin type 2 (TRPM2) is a redox-sensitive, calcium-permeable cation channel activated by various signals, such as adenosine diphosphate ribose (ADPR) acting on the ADPR pyrophosphatase (ADPRase) domain, and cyclic ADPR. Here, we purified the FLAG-tagged tetrameric TRPM2 channel, analyzed it using negatively stained electron microscopy, and reconstructed the three-dimensional structure at 2.8-nm resolution. This multimodal sensor molecule has a bell-like shape of 18 nm in width and 25 nm in height. The overall structure is similar to another multimodal sensor channel, TRP canonical type 3 (TRPC3). In both structures, the small extracellular domain is a dense half-dome, whereas the large cytoplasmic domain has a sparse, double-layered structure with multiple internal cavities. However, a unique square prism protuberance was observed under the cytoplasmic domain of TRPM2. The FLAG epitope, fused at the C terminus of the ADPRase domain, was assigned by the antibody to a position close to the protuberance. This indicates that the agonist-binding ADPRase domain and the ion gate in the transmembrane region are separately located in the molecule.