Interactions of Arsenic with Human Metallothionein-21

Arsenic is a toxic element that is found in the atmosphere, as well as in aquatic and ter-restrial environments. We have demonstrated that As3 * binds to human metallothionein-2 (hMT-2) by UV absorption spectroscopy, inductively coupled plasma-atomic emission spectrometry (ICP-AES), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). MALDI-TOF-MS revealed that the structure of the adduct formed by arsenic and hMT-2 (As-hMT-2) was not homogeneous. The maximum molar ratio of arsenic to hMT-2 was found to be more than 6:1 on ICP-AES, UV absorp-tion spectroscopy and MALDI-TOF-MS. The ratio of the number of sulfhydryl groups in hMT-2 that bound arsenic was 3:1, which is the same as the ratios reported previously for arsenic-glutathione and arsenic-phytochelatin complexes. Key words: arsenic, heavy metal binding protein, human metallothionein, MALDI-TOF-MS. Arsenic is a toxic element that is found ubiquitously in the environment. Substantial amounts of arsenic are released as a result of geological activity, and as a result of the dis