PHYLOGENETIC RELATIONSHIPS IN ZnT SUPERFAMILY OF ZINC ION TRANSPORTERS IN SILICO

The Zinc transporter (ZnT superfamily) facilitates Zn-transport into intracellular vesicles in life forms. Existing database has been enriched with the identification of new Zn-transporters important for therapeutic and intra-channel metal binding capacity. The present work uses a consensus sequence approach to identify extra-membrane metal-binding motif in Zn transporter protein family. Molecular phylogeny among members of ZnT superfamily proteins was analyzed. In all 166 representative sequences covering all known members of ZnT protein subfamilies (subgroups Znt1-Znt10) from bacteria, archaea and eukarya were selected and used to obtain ten consensus sequences, each representing a specific ZnT subgroup (1-10). Using bioinformatics tools a phylogenetic tree was constructed to explore the evolutionary link between the various ZnT subgroup considering members from lower and higher life forms. The unrooted phylogenetic tree obtained by Clustal W and NJ method revealed the existence of three clearly separated clades, which were segregated early in the evolution of this superfamily. Consensus sequence analysis using Weblogo revealed motifs of (HX)n type that evolved to bind the Zn ions effectively, enabling Zn transport. No significant similarity among members of Znt1 and Znt10 or Znt2 and Znt10 suggest that gene duplication event in the ZnT superfamily gene probably occurred in the later phase of evolution when individual specificities of the distinguished ZnT subgroups were already formed.