Evolutionary Mode of Metallothioneins Inferred from Cd-MT Genes of Tetrahymena
摘要
From Tetrahymena thermophila (strain BFS),the coding region of Cd-MT gene was cloned and sequenced,and identified as MTT1 isoform. A serial duplicate structure is discovered in its amino acid sequence, which separates the coding region into three parts (Part 1: 7-61; Part 2: 64-118;Part 3: 122-162). The alignments among them and comparison with the corresponding parts of MT1 isoform suggest that MT1 and MTT1 isoforms both come from the same ancient gene that is homologous to Part 1, and Cd-MTs of Tetrahymena are aroused by such ancient gene duplication. The prediction of secondary structures and the analysis of the disulfide-bonding state of cysteine show that there are a lot of differences between MT1 and MTT1 isoforms, which maybe relate to their function mechanism.