Human ATP Binding Cassette (ABC) Transporters: A Phylogenetic Investigation

"Till date the largest known family of transporters is ABC transporter superfamily. The genes that encode ABC genes are widely dispersed in genome and show a high degree of amino acid sequence identity among eukaryotes. Phylogenetic analysis has allowed the gene superfamily divided into seven subfamilies containing 49 members of proteins in human. Despite the immense amount of biochemical studies, and recent advances in the visualization of ABC transporters, answers to critical questions about their translocation mechanisms have remained elusive. Hence, genomic identification of these transporters will allow choosing correct molecule based on their genomic heterogeneity and mode of behavior in human. The full amino acid sequences of all known seven subfamilies of human ABC transporter proteins were retrieved from NCBI website. Phylogenetic analysis was performed using “Phylogeny.fr”. The topologies of the full (ABCB1) and half ABC (ABCG2) transporters were identified using TOPCONS consensus prediction. Secondary structures of full (ABCB1) and half (ABCG2) ABC transporters were also predicted by Protter. Our analysis showed that ABC proteins are a highly dynamic group that has undergone a significant diversification after the divergence of human species. High gene loss events were observed during the process of gene duplication and this resulted in a great variety of different subfamily of ABC proteins in human. A remarkable variation was observed in the members of the full-length transporters as compared to half-size transporters. The present study can be used for classifying human transporters from other individuals and for a further in-depth characterization of members of these highly important groups. "