Lanthanum(III) Impacts on Metallothionein MTT1 and MTT2 from Tetrahymena thermophila Qinglu Wang & Jing Xu & Yajing Zhu & Baofeng Chai & Aihua Liang & Wei Wang Received: 13 December 2010 / Accepted: 13 February 2011 # Springer Science+Business Media, LLC 2011 Abstract Metallothionein MTT1 and MTT2 from Tetrahymena thermophila are sulfydryl-rich proteins that can bind to and are inducible by heavy metals such as mercury, cadmium, zinc, and copper. However, little is known about the induction and binding of T . thermophila metallothionein by trivalent metals. In this study, we found that 10–80 μM La 3+ can promote Tetrahymena cells proliferation, and fluorescence spectrum analysis showed that La 3+ can enter T . thermophila cells. Real-time quantitative polymerase chain reaction showed La 3+ induced the expression of MTT1 and MTT2. Furthermore, Fluorescence analysis indicated La 3+ bind to MTT1 and MTT2. These results implied that La 3+ could interact with MTT1 and MTT2 via aspartic or glutamic acid oxygen atoms. Keywords Metallothionein . La 3+ . MTT1 . MTT2 . Tetrahymena thermophila Introduction Rare earth elements (REEs) include 15 elements in the Periodic Table, including lanthanide and actinide, plus yttrium (Y) and scandium (Sc). REEs are naturally present in the environment, and some of them, mainly La and Ce, are fairly abundant in nature despite of their name (the term “rare earth” derives from the misconception that they exhibit low natural abundance). However, they exist only in trace amounts in biological systems [1]. REEs have been widely used in functional materials, catalysts, and some fertilizers in agriculture, especially in China. Consequently, more and more REEs get into the environment and finally enter the human body through the food chain [2]. A large number of studies on their toxicological effects have been reported. The studies on the toxicology of La 3+ showed that La 3+ had adverse effects on various organs as well as the liver and nervous system of animals, e.g., the lesion caused by La 3+ showed oxidative stress, Biol Trace Elem Res DOI 10.1007/s12011-011-9004-2 Q. Wang : J. Xu : Y. Zhu : B. Chai : A. Liang : W. Wang (*) Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, 92 Wucheng Rd, Taiyuan 030006, People’ s Republic of China e-mail: gene@sxu.edu.cn