Study of metal-containing proteins in the roots of Elsholtzia splendens using LA-ICP-MS and LC–tandem mass spectrometry

In the present study, the metal-containing proteins in the roots of Cu-tolerant plant Elsholtzia splendens were investigated. The proteins from the plant roots were extracted and separated by two-dimensional gel electrophoresis (2D GE). Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to screen metal-containing proteins on the dried 2D gels. Images of Cu, Zn, Na, Mg, K, Ca, Mn, Fe, P and S, and also of Ag, were obtained by scanning the gel (line by line) using the LA-ICP-MS techniques developed in our laboratory. Cu-, Zn- and Mg-containing proteins were found in the gel sections of interest via LA-ICP-MS imaging. These protein spots were then in-gel digested with trypsin and analyzed by liquid chromatography tandem mass spectrometry (LC–MS/MS) for identification. The mechanisms involved in Cu tolerance and accumulation were also discussed.