Deep Learning Exploration Expands the Natural Diversity of Metallothioneins in the Archaea Domain

The diversity and functions of metallothioneins (MTs) in Archaea remain poorly understood. This study identifies 180 archaeal MTs from 406 genomes, revealing distinct evolutionary lineages and structural diversity. Phylogenetic analysis suggests a novel class with divergent ancestry. AlphaFold3-based modeling highlights conserved Cys-rich motifs and irregular structures, potentially enhancing adaptation to extreme environments. Functional assays show that four MTs (MT334126, MT382228, MT114104, and MT282443) increase cadmium resistance, while MT334126 and MT382228 also enhance copper resistance. Targeted mutations at key sites boost metal adsorption, validated by structural modeling. This work provides the first comprehensive insight into archaeal MTs, laying the foundation for environmental and biotechnological applications.