RESULTS: A bioinformatics study was performed to investigate the phylogenetic relationship among the
bestrophin family members and to statistically evaluate sequence conservation and functional divergence. Phylogenetic tree assembly with all available eukaryotic
bestrophin sequences suggests gene duplication events in the lineage leading to the vertebrates. A common N-terminal topology which includes four highly conserved transmembrane domains is shared by the members of the four paralogous groups of vertebrate
bestrophins and has been constrained by purifying selection. Pairwise comparison shows that altered functional constraints have occurred at specific
amino acid positions after phylogenetic diversification of the paralogues. Most notably, significant functional divergence was found between
bestrophin 4 and the other family members, as well as between
bestrophin 2 and
bestrophin 3. Site-specific profiles were established by posterior probability analysis revealing significantly divergent clusters mainly in two hydrophilic loops and a region immediately adjacent to the last predicted transmembrane domain. Strikingly,
codons 279 and 347 of human
bestrophin 4 reveal high divergence when compared to the paralogous positions strongly indicating the functional importance of these residues for the
bestrophin 4
protein. None of the functionally divergent
amino acids were found to reside within obvious sequences patterns or motifs.
CONCLUSION: