Two new members of the Tetrahymena multi-stress-inducible metallothionein family: characterization and expression analysis of T. rostrata Cd/Cu metallothionein genes.

We report the cloning and characterization of two new metallothionein (MT) genes (TrosMTT1 and TrosMTT2), isolated as cDNAs, from the ciliated protozoa Tetrahymena rostrata. The TrosMTT1 inferred protein has been identified as a CdMT and included into the 7a subfamily of Tetrahymena MTs, while TrosMTT2 has been identified as a CuMT (including it into 7b subfamily), due to its similarity to TpigMT-2 and its significant induction by copper. TrosMTT1 protein sequence reveals a remarkably regular and hierarchical modular organization, as it is known for other Tetrahymena CdMTs, showing a bi-modular structure.