Mechanisms of heavy metal cation homeostasis in marine invertebrates

1. The main mechanisms involved in heavy metal cation homeostasis in marine invertebrate cells are described. 2. Metallothioneins are probably the most important soluble compounds involved in heavy metal cation homeostasis. The biochemical characteristics of these metalloproteins and the relationship between their amino acid composition and heavy metal binding capacity are elucidated. Moreover data are reported concerning the physiological role of metallothioneins e.g. heavy metal detoxification, cellular metal redistribution, free radical scavenger action, etc. The possible meaning of different soluble compounds in heavy metal cation homeostasis is also discussed. 3. The biochemical role of lysosomes in heavy metal cation compartmentalization and the involvement of these organelles in metallothionein accumulation and sequestration are shown. 4. Data are reported concerning the sequestration of heavy metal cations in insoluble granules as a mechanism of metal detoxification.