Major facilitator superfamily is one of the largest superfamily of secondary transporters present across the kingdom of life. Considering the physiological and clinical importance of MFS proteins, we attempted to explore the phylogenetic and structural aspects of the superfamily. To achieve the objectives, we performed global sequence-based analyses of MFS proteins encompassing multiple taxa. Notably, phylogenetic analysis of MFS proteins resulted in the clustering of MFS proteins based on their function, rather than lineage of the respective organisms. Additionally, we employed information theoretic measures, Relative entropy (RE) and Cumulative relative entropy (CRE) to decipher fold-specific and function-specific residues, respectively, in the MFS proteins. The residues with high RE score when mapped on to the 3D-structure of MFS transporter LacY, were found to be distributed throughout the tertiary structure of the protein. On the other hand, CRE calculation was employed to contrast two subfamilies Drug H+ antiporter 1 and 3 (DHA1 and DHA3). The particular analysis unveiled certain differentially conserved residues in DHA1 as compared to DHA3 highlighting family-specific importance of them. Remarkably, a number of high scoring CRE residues have already established functional roles, for instance, the arginine residue present in TMH4. Altogether, the current study apart from providing an insight into the functional clustering of MFS proteins also identifies residues with established or plausible roles in the transport mechanism. Thus, the study lays a platform for future structure-function studies of these proteins.
Keywords: Cumulative relative entropy; Major facilitator superfamily; Phylogeny; Relative entropy; Sequence conservation.